HK1161448B - Fault locator for long haul transmission system - Google Patents

Description

Fault locator for long-range transmission system

Background

Fiber optic cables are often used for high speed communications and data transmission over long distances. Currently, long haul optical fiber transmission networks may extend over distances of 4000km, and possibly longer distances. In fiber optic cables, electrical signals from a communication signal source (e.g., a telephone or data modem) are modulated into light waves and transmitted via a fiber optic connection to a receiver, where they are recovered by demodulation processing. A key factor in implementing fiber optic technology is the attenuation or signal loss characteristics of the fiber optic cable used as the transmission medium. Signals transmitted over fibre channels are attenuated over long distances and reach a sufficiently low level at a distance from the signal source to require amplification by repeaters inserted in the fibre channels. Repeater sites on long haul optical fiber transmission lines are typically spaced apart by an interval of 80km to 160km for reasons including loss characteristics of the optical fiber cable and other physical conditions.

For large-scale fiber optic networks, the optical fibers are occasionally subject to interference or failure for a variety of reasons. For example, fiber optic cables may be cut accidentally; aging of the fiber optic cable can degrade transmission capabilities, resulting in diminished optical signals; and kinks in the fiber optic cable can attenuate or interfere with the optical signal. To repair a fault in a long haul transmission line, the fault must be located and a field team dispatched to the location of the fault. Due to the long distances of long haul fiber optic networks, field maintenance teams may work hours and days just to locate the fault before they can repair the line. Instruments using Optical Time Domain Reflectometry (OTDR) are effective in locating faults in fiber optic cables. However, OTDR can only work for one interval due to the property that the amplifier in a long haul fiber system will block any reflections, whereas a long haul system may have as many as 20 intervals. Furthermore, the loss of signal due to a fault may trigger an automatic shutdown of the amplifier closest to the fault, thereby preventing signals, including OTDR signals, from being transmitted through the affected amplifier. Thus, locating a fault in a long haul transmission network alone may require field teams to travel to the location of multiple repeaters, where each repeater location may be as far as 160km from the next repeater. Furthermore, faults in long haul fiber optic systems may be underground and, therefore, not visible by visual inspection. OTDRs may be employed at amplifiers at repeater sites at both ends of a zone containing a fault to locate the fault more accurately than a single OTDR and thus minimize the cost of locating, repairing and/or splicing the fault. However, such techniques necessarily require more OTDRs for more locations.

Drawings

FIG. 1 is a diagram illustrating an exemplary long haul optical fiber transmission network;

FIG. 2 is a diagram illustrating an exemplary long haul fiber optic transmission network incorporating a system for remotely locating faults;

FIG. 3 is a diagram illustrating an exemplary modified optical time domain reflectometry instrument in the system described herein;

FIG. 4 is a diagram of an exemplary configuration of an exemplary automated fiber patch panel that may be employed in the network of FIG. 2;

FIG. 5 is a pictorial illustration of an exemplary configuration of another exemplary automated fiber optic patch panel that may be employed in the network of FIG. 2;

FIG. 6 is a flow diagram of an exemplary process 600 for locating a fault in the exemplary long-haul network of FIG. 2;

FIG. 7 is a diagram of exemplary signal paths in the exemplary long-range network of FIG. 2;

FIG. 8 is a diagram of exemplary signal paths in the exemplary long-range network of FIG. 2;

fig. 9 is a diagram of an exemplary configuration of the exemplary long-range network of fig. 2.

Detailed Description

The following detailed description refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. Also, the following detailed description does not limit the invention.

Embodiments described herein may allow a fiber optic network operator to locate faults in a long haul network from a single remote location.

Fig. 1 is a diagram illustrating an exemplary long haul fiber optic network 100. An exemplary long-haul fiber optic network 100 may include long-haul lines 105 transmitting in a first direction and parallel long-haul lines 110 transmitting in the opposite direction of the long-haul lines 105. Although fig. 1 shows a particular number and configuration of components, long-range network 100 and long-range lines 105 and 110 may include more, fewer, different, or otherwise configured components than shown in fig. 1. The components and operation of the long-range line 105 may be similar to those of the long-range line 110, with the only significant difference being the direction of the signals transmitted on the two lines. Exemplary long-range lines 105 and 110 may each include an emitter 115 and a wavelength division multiplexer 120 located at a first end of the long-range lines 105 and 110. The long-range lines 105 and 110 may further include a plurality of amplifiers 130 and fiber optic cables 125 between the first ends of the long-range lines 105 and 110 and the second ends of the long-range lines 105 and 110, at which the wavelength division demultiplexer 135 and the receiver 140 may be disposed.

As shown in fig. 1, in one embodiment, optical signals from a group of transmitters 115 may be sent to a wavelength division multiplexer 120 where multiple input signals may be multiplexed into a single output signal for transmission over fiber optic cable 125 in an exemplary long haul line 105 or 110 operating in an exemplary long haul fiber optic network 100. The exemplary long-haul fiber optic network 100 may include a plurality of wavelength division multiplexers 120 for each long-haul line.

A plurality of amplifiers 130 may be intermittently spaced along the exemplary long-range lines 105 and 110 to increase signal strength sufficiently to travel along the entire length of the long-range network 100. In an exemplary long-range network, the distance between amplifiers 130 may be as large as 160 km. As shown in fig. 1, when the wavelength division multiplexed signal has traveled the entire length of the long-range line 105 or 110, the signal may be processed by a wavelength division demultiplexer 135, where the single multiplexed input signal may be split into multiple signals for transmission to a receiver 140. In either exemplary long-range line 105 or 110, the signal transmitter 115 and the signal receiver 140 may be integrated into a single piece of hardware. Similarly, in either exemplary long-range line 105 or 110, the wavelength division multiplexer 120 and the wavelength division demultiplexer 140 may be integrated in a single piece of hardware. Further, in the exemplary fiber optic network 100, the transmitter 115, the wavelength division multiplexer 120, the wavelength division demultiplexer 135, and the receiver 140 may be located at a central location, such as a network operations center.

As shown in fig. 1, a fault 145 may occur between two amplifiers 130 in a long-range line 105, interfering with signal transmission in that line. In the exemplary fiber optic long haul network 100, Optical Time Domain Reflectometry (OTDR) instrumentation 150 may be employed to locate the fault. OTDR may include transmitting an optical pulse or series of optical pulses of known wavelength at a point along the exemplary long haul line 105, and then measuring the portion of the light reflected back from the same point in the exemplary long haul line 105. The intensity of the reflected light is measured and integrated as a function of time and plotted as a function of fiber length. Thus, OTDRs can be used to locate faults in fiber lines, and to estimate fiber and connection losses. In the exemplary fiber optic long haul network 100, the amplifier 130 blocks OTDR pulses and reflections. In addition, fault 145 may cause an automatic shutdown of long haul line 105. For example, the fault 145 may result in sufficient signal loss to trigger an automatic shutdown of the amplifier 130 on either side of the fault 145. Therefore, in order to detect and locate the fault 145, OTDR instruments 150 may be employed at the amplifiers 130 at both ends of the interval in which the fault 145 is located.

Fig. 2 is a diagram illustrating an exemplary long haul fiber optic transmission network 200 incorporating a system for remotely locating faults. An exemplary long haul fiber optic transmission network 200 may include long haul lines 205 for transmission in a first direction, and long haul lines 210 for transmission in a second direction opposite the first direction, modified OTDR instruments 245 and OTDR patch panels 250 installed at end locations of the long haul lines 205 and 210, and a set of automatic fiber patch panels 255 connected at specific intermediate locations on the long haul lines 205 and 210.

The long haul line 205 may include a set of transmitters 215, a multiplexer 220, a fiber optic cable 225, a set of amplifiers 230, a demultiplexer 235, and a set of receivers 240. The long-haul line 210 may also include a set of transmitters 215, a multiplexer 220, a fiber optic cable 225, a set of amplifiers 230, a demultiplexer 235, and a set of receivers 240.

The transmitter 215 may generally be considered a light source and may include any device that is modulated using an electrical signal and generates an optical signal. In one embodiment, the transmitter 215 may include a laser that may generate and transmit optical signals at a particular wavelength. For example, a group of emitters 215 may output a plurality of spatially separated optical signals at different wavelengths to the wavelength division multiplexer 220.

The wavelength division multiplexer 220 may be any device that combines the separate optical input signals into a single optical output signal. In one embodiment, the wavelength division multiplexer 220 may receive a plurality of spatially separated optical signals from the transmitter 215 and combine the separated signals to produce a combined output signal for transmission over the fiber optic cable 225.

Fiber optic cable 225 may be any medium for transmission of optical signals. In one embodiment, fiber optic cable 225 receives the optical signals from wavelength division multiplexer 220 and transmits the signals to amplifier 230.

Amplifier 230 may include any device capable of increasing the intensity or amplitude of an input optical signal while maintaining a wavelength. In one embodiment, the plurality of amplifiers 230 may be intermittently spaced along the long-range lines 205 and 210 to increase the signal strength sufficiently to travel along the entire length of the long-range lines 205 and 210.

The wavelength-division demultiplexer 235 may be any device that receives an input optical signal including various wavelengths and spatially separates the component wavelengths to have an output signal at each component wavelength. In one embodiment, demultiplexer 235 receives the optical signal from amplifier 230 and transmits the output signal at the component wavelengths to optical receiver 240.

Optical receiver 240 may include any device that receives an input optical signal and modulates an output electrical signal with the input optical signal, including a charged coupled device and/or a photodetector. In one embodiment, optical receiver 240 receives an input optical signal and uses the optical signal to modulate electrical signals including video and telephony transmissions.

Modified OTDR instrument 245 may include pulsed and/or continuous light generation functionality for managing optical time domain reflectometry on exemplary long haul lines 205 and 210. The modified instrument 245 may also include a continuous optical signal generation function to prevent automatic laser shut down of the amplifier 230. In this case, modified OTDR instrument 245 may also include wavelength coupling and signal splitting functionality to combine and separate the OTDR signal and the continuous optical signal as described in detail later with reference to fig. 3.

OTDR patch panel 250 may include any means for receiving OTDR signals from an OTDR signal generator and transmitting the OTDR signals to locate faults in fiber link intervals adjacent to OTDR patch panel 250. In one embodiment, OTDR patch panel 250 may include an optical circulator to transmit OTDR signals from modified OTDR instrument 245 to a fault on line 205 or line 210, while transmitting reflected OTDR signals from a fault on line 205 or line 210 to modified OTDR instrument 245.

Automatic fiber patch panel 255 may include any device capable of receiving a combined OTDR signal and a continuous optical signal from exemplary modified OTDR instrument 245 and transmitting the combined OTDR signal through exemplary amplifier 230. In one embodiment, the automated fiber optic patch panel includes wavelength coupling and splitting functionality and optical recycling functionality in a configuration that will be described later with reference to fig. 4 and 5.

Although fig. 2 shows a particular number and configuration of components, long-range network 200 and long-range lines 205 and 210 may include more, fewer, different, or additional configurations of components than shown in fig. 2. The components and operation of the long-range line 205 may be similar to those of the long-range line 210, with the only significant difference being the direction of the signals transmitted on the two lines. As shown in fig. 2, long-range network 200 may include a transmitter 215, a wavelength division multiplexer 220, a wavelength division demultiplexer 235, and an optical receiver 240 located at the ends of long-range lines 205 and 210. The term "end" may refer to any location having an optical transmitter and/or receiver. In one embodiment, the terminal may further include a wavelength division multiplexer and a wavelength division demultiplexer. In further embodiments, the end may be located where the operation of the entire network may be monitored and controlled. In this case, the endpoints of both long haul lines 205 and 210 may be located at a network operations center.

In still other embodiments, one or more components of exemplary long-range network 200 may perform one or more tasks described as being performed by one or more other components of exemplary long-range network 200. Moreover, one or more components of the exemplary long-haul network 200 may be located outside of the exemplary long-haul network 200, or components may be distributed throughout the network described herein.

FIG. 3 is a diagram illustrating components of an exemplary modified optical time domain reflectometry instrument 245 in the system described herein. Exemplary modified OTDR instrument 245 may include OTDR transmitter 310, continuous optical signal generator 320 and wavelength coupler 330, wavelength decoupler 340, OTDR receiver 350, optical dump (optical dump) 360, and central processing unit 370. OTDR transmitter 310 may include any means for generating an optical signal for use in optical time domain reflectometry. For example, OTDR transmitter 310 may include a device capable of transmitting an optical pulse, a series of optical pulses, or a continuous optical signal at a known wavelength and signal strength in order to measure reflected signals in the OTDR.

The continuous optical signal generator 320 may include any device capable of generating and transmitting a continuous optical signal, such as a laser. In one embodiment, continuous optical signal generator 320 may be capable of generating a continuous optical signal having a wavelength and signal strength designed to prevent automatic laser shutdown of one or more amplifiers 230.

Wavelength coupler 330 may include any device capable of combining two or more optical signals and outputting a single combined optical signal, including a multiplexer. In one embodiment, wavelength coupler 330 may include a device capable of combining optical signals by wavelength.

Wavelength decoupler 340 may comprise any device capable of receiving an input optical signal and splitting the signal to produce two or more output signals, such as a splitter or demultiplexer. In one embodiment, the wavelength decouplers may include means capable of separating the combined optical signals by wavelength.

OTDR receiver 350 may include any device, including a photosensor and/or photodetector, that receives an input optical signal and modulates an output electrical signal using the input optical signal. In one embodiment, OTDR receiver 350 receives a reflected signal used in optical time domain reflectometry and uses the reflected signal to calculate the distance to the reflection source.

Optical emptier 360 may include any optical element that receives and absorbs an input optical signal. In one embodiment, optical emptier 360 may include a device designed to receive the laser signal while preventing reflection of the laser signal.

The central processing unit 370 may be any computing device capable of executing a computer program. In one embodiment, the central processing unit 370 may include a microprocessor including a stored program for calculating distance based on a comparison of data from signals transmitted and received at known wavelengths.

In operation of exemplary modified OTDR instrument 245, exemplary OTDR transmitter 310 may generate an optical pulse, a series of optical pulses, and/or a continuous OTDR signal. Exemplary OTDR transmitter 310 may generate wavelength λ₁The OTDR signal of (a). For example, wavelength λ₁May be a known wavelength for performing optical time domain reflectometry.

Further, in the example modified OTDR instrument 245, the continuous optical signal generator 320 may generate a continuous optical signal. The continuous optical signal of the continuous optical signal generator 320 may be, for example, a wavelength λ₂This is measured with lambda₁Distinct wavelengths. In one embodiment of the continuous optical signal generator 320, at a wavelength λ₂The generated continuous signal may be a laser emission of a particular signal strength and wavelength designed to prevent automatic laser shutdown of the example amplifier 230 and/or automatic laser shutdown of the example long-range network 200. For example, a fault on any long haul line in long haul network 200 may trigger an automatic shutdown of amplifiers located on either side of the fault.

Wavelength coupler 330 may receive as inputs an OTDR signal from exemplary OTDR transmitter 310 and a continuous optical signal from continuous optical signal generator 320. In one embodiment, wavelength coupler 330 may combine the input signals to produce a transmission wavelength λ₁And wavelength lambda₂Output signal of. In this case, the output signal from wavelength coupler 330 may include a wavelength λ used to locate a fault in exemplary long-range network 200₁And a wavelength lambda for preventing automatic laser shutdown of the exemplary long-haul network 200₂Of the optical signal. In one embodiment, wavelength coupler 330 may transmit the combined signal to the closest amplifier 230 on long-range links 205 and/or 210 (fig. 2).

Wavelength decoupler 340 may receive an input signal comprising a plurality of wavelengths and separate the input signal into a plurality of output signals of component wavelengths. In one embodiment, the input signal may be received from the closest amplifier on long-range link 205 and/or 210 and may include a wavelength λ₁Of the OTDR signal and wavelength lambda₂Of the optical signal. Wavelength decoupling device 340 can decouple wavelength λ₁Of the OTDR signal and wavelength lambda₂Are separated. The wavelength decoupling device can decouple the wavelength lambda₁Is directed to the optical receiver 350, and the wavelength decouplers may direct the wavelength lambda to the optical receiver₂Is directed to optical emptier 360. Wavelength λ directed to exemplary OTDR receiver 350₁May be a wavelength λ generated by OTDR transmitter 310₁Reflection of the OTDR signal of (1). Wavelength λ of guided light emptier 360₂May be the wavelength λ generated by the continuous optical signal generator 320₂Of the optical signal.

Central processing unit 370 may receive input signals from OTDR transmitter 310 and OTDR receiver 350. In one embodiment, the central processing unit may receive signal strength information from OTDR transmitter 310 and OTDR receiver 350, which central processing unit 370 may use to generate an output of a computer program stored in the central processing unit. For example, OTDR receiver 350 may receive wavelength λ generated by OTDR transmitter 310₁Reflection of the OTDR signal of (1). In this case, central processing unit 370 may use signal strength information from OTDR transmitter 310 and OTDR receiver 350 to determine the wavelength λ₁Of an OTDRDistance of the reflection source of the sign.

Although fig. 3 shows exemplary components of exemplary modified OTDR instrument 245, in other embodiments, exemplary modified OTDR instrument 245 may contain more, fewer, different, or otherwise configured components than those shown in fig. 3. In still other embodiments, one or more components of exemplary modified OTDR instrument 245 may perform the tasks described as being performed by one or more other components of exemplary modified OTDR instrument 245. Moreover, one or more components of exemplary modified OTDR instrument 245 may be located outside of exemplary modified OTDR instrument 245, or components may be distributed throughout the system described herein.

Fig. 4 is a diagram illustrating the components of an exemplary automated fiber patch panel 255. Exemplary automatic patch panel 255 may be located at the input and output sides of amplifier 230 and may include wavelength decoupler 410, optical circulator 420, and wavelength coupler 430. Wavelength decoupler 410 may comprise any device capable of receiving an input optical signal and splitting the signal to produce two or more output signals, such as a splitter or demultiplexer. In one embodiment, wavelength decoupler 410 may comprise a device capable of combining optical signals by wavelength splitting. For example, wavelength decoupler 410 may switch between split and non-split operation. In one embodiment, a particular signal input may switch wavelength decoupler 410 to a signal splitting operation. In this case, the wavelength λ₁May automatically trigger the signal splitting operation of wavelength decoupler 410.

The optical circulator 420 may include any device capable of splitting optical signals received from opposite directions in a single optical fiber. In one embodiment, the optical circulator 420 may receive a transmitted signal in one direction and a reflection of the same signal in the opposite direction. For example, the optical circulator 420 may receive the wavelength λ in a first direction₁And receives the wavelength lambda in the opposite direction₁The reflected OTDR signal of (a).

Wavelength coupler 430 may be any device capable of combining two or more optical signals and outputting a single combined optical signal. In one embodiment, wavelength coupler 430 may include a device capable of combining optical signals by wavelength, such as a multiplexer.

As shown in fig. 4, exemplary automatic fiber patch panels 255 may be located on the input and output sides of the exemplary amplifier 230. Functionally, automatic fiber patch panel 255 may operate in several modes. In the first or idle mode, automatic fiber patch panel 255 may not perform signal processing at all. For example, assume there is no failure in long-haul network 200. In this case, the optical signal may be transmitted over the entire length of the long haul lines 205 and 210 without signal processing performed by the automated fiber patch panel 255 at the location of any repeater amplifier 230. Further, as long as amplifier 230 at the location of automatic fiber patch panel 255 is not affected by a fault in an adjacent segment of the long-haul link, automatic fiber patch panel 255 may continue to operate in the first or idle mode. For example, assume that a failure has occurred between the first and second amplifiers 230 of the long-range link 205. In this case, all automatic fiber patch panels on the long-haul link 205 that are not located at either the first or second amplifier 230 may operate in idle mode because only the first and second amplifiers 230 may be affected by the fault.

In one embodiment, the automatic fiber patch panel 255 may be switchable. For example, automatic fiber patch panel 255 may be automatically switchable. It is assumed that amplifier 230 is not operating due to an automatic laser shutdown caused by a failure on the fiber link section adjacent to it. In such a case, automatic fiber patch panel 255 at affected amplifier 230 may automatically switch from the first or idle mode to the second or operational mode upon arrival of a signal comprising wavelength λ that modified OTDR instrument 245 (fig. 2 and 3) has transmitted₁The OTDR signal of (a).

In addition to the first or idle mode, automatic fiber patch panels 255 may operate in different configurations during operation, depending on the direction of the plurality of signals being processed. Fig. 4 is a diagram illustrating an automatic fiber patch panel operating in an exemplary operating mode in the exemplary long haul network 200 described herein. While the illustration of exemplary automatic fiber patch panel 255 in fig. 4 may be described as an operational mode, such description is not intended to limit the functionality or application of exemplary automatic fiber patch panel 255. Rather, this description is intended only to indicate that exemplary automatic fiber patch panel 255 can handle optical signals in multiple directions.

In one embodiment, the input signal to exemplary amplifier 230 may include a combined OTDR signal 400 from modified OTDR instrument 245 (fig. 2 and 3). For example, as described with respect to fig. 3, combined OTDR signal 400 may include a wavelength λ₁Of the OTDR signal and wavelength lambda₂Of the optical signal. In this case, amplifier 230 may transmit combined OTDR signal 400 to wavelength decoupler 410, which may separate the component signals of combined OTDR signal 400. In one embodiment, wavelength decoupler 410 may decouple wavelength λ₁The OTDR signal of (a) is transmitted to the optical circulator 420. In this case, optical circulator 420 may transmit wavelength λ as signal 440₁To locate faults in the exemplary long haul network 200. Further in operation of automatic fiber patch panel 255, wavelength decoupler 410 can couple wavelength λ₂To wavelength coupler 430.

Assume that transmitted signal 440 includes a wavelength λ₁And the signal 440 has experienced a fault. Now assume that the fault produces a wavelength λ in the opposite direction of the signal 440 transmitted from the optical circulator 420₁The reflected OTDR signal of (a). In this case, the signal 440 may include a wavelength λ transmitted in one direction₁And a reflected wavelength λ in the opposite direction₁The OTDR signal of (a). The optical circulator 420 may receive the wavelength λ₁And directs the reflected OTDR signal to wavelength coupler 430. Wavelength coupler 430 may couple wavelength λ₁Reflected OTDR signal and wavelength lambda of₂Can be combined, wavelength coupler 430 can receive the wavelength lambda from wavelength decoupler 410₂Of the optical signal. Wavelength coupler 430 may include a wavelength λ₁Reflected OTDR signal and wavelength lambda of₂The combined OTDR signal of the continuous optical signals is directed to amplifier 230 for transmission as output optical signal 450. Amplifier 230 may direct output signal 450 to modified OTDR instrument 245 (see fig. 2 and 3).

Although fig. 4 illustrates exemplary components of exemplary automatic fiber patch panel 255, in other embodiments, exemplary automatic fiber patch panel 255 may contain more, fewer, different, or otherwise configured components than those illustrated in fig. 4. In still other embodiments, one or more components of exemplary automatic fiber patch panel 255 may perform tasks described as being performed by one or more other components of exemplary automatic fiber patch panel 255. Moreover, one or more components of exemplary automatic fiber patch panel 255 may be located outside of exemplary automatic fiber patch panel 255, or the components may be distributed throughout the system described herein.

Fig. 5 is a diagram illustrating components of an exemplary automatic fiber patch panel 255 operating in an exemplary operating mode in the exemplary long haul network 200 described herein. While the illustration of exemplary automatic fiber patch panel 255 in fig. 5 may be described in terms of modes of operation, such description is not intended to limit the functionality or application of exemplary automatic fiber patch panel 255. Rather, this description is intended only to indicate that exemplary automatic fiber patch panel 255 can handle optical signals in multiple directions.

As shown in fig. 5, exemplary automatic fiber patch panel 255 may be located on both the input and output sides of exemplary amplifier 230 and may include wavelength decouplers 510, optical circulators 520, and wavelength couplers 50. Wavelength decoupler 510 may include a band-gap filter capable of receivingAny device that inputs an optical signal and splits the signal to produce two or more output signals, such as a splitter or demultiplexer. In one embodiment, wavelength decoupler 510 may comprise a device capable of combining optical signals by wavelength splitting. For example, the wavelength decoupler can switch between split and non-split operation. In one embodiment, a particular input signal may switch wavelength decoupler 510 to a signal splitting operation. For example, wavelength λ₁May automatically trigger the signal splitting operation of wavelength decoupler 510.

The optical circulator 520 can include any device capable of separating optical signals received from opposite directions in a single optical fiber. In one embodiment, the optical circulator 520 may receive a transmitted signal in one direction and a reflection of the same signal in the opposite direction. For example, the optical circulator 520 may receive the wavelength λ in a first direction₁And receives the wavelength lambda in the opposite direction₁The reflected OTDR signal of (a).

Wavelength coupler 530 may be any device capable of combining two or more optical signals and outputting a single combined optical signal. In one embodiment, wavelength coupler 530 may include a device capable of combining optical signals by wavelength, such as a demultiplexer.

In one embodiment, the input signal to exemplary amplifier 230 may include a combined OTDR signal 500 from modified OTDR instrument 245 (fig. 2 and 3). For example, as described with respect to fig. 3, combined OTDR signal 500 may include wavelength λ₁Of the OTDR signal and wavelength lambda₂Of the optical signal. In this case, amplifier 230 may transmit combined OTDR signal 500 to wavelength decoupler 510, which may separate the component signals of combined OTDR signal 500. In one embodiment, wavelength decoupler 510 may decouple wavelength λ₁The OTDR signal of (a) is transmitted to the optical circulator 520. In this case, optical circulator 520 may transmit wavelength λ as signal 540₁To locate exemplary OTDR signalsA failure in the long haul network 200. Further in operation of automatic fiber patch panel 255, wavelength decoupler 510 can decouple wavelength λ₂Is transmitted to wavelength coupler 530.

Assume that transmitted signal 540 includes a wavelength λ₁And the signal 540 has experienced a fault. Now assume that the fault produces a wavelength λ in the opposite direction of the signal 540 transmitted from the optical circulator 520₁The reflected OTDR signal of (a). In this case, signal 540 may include a wavelength λ transmitted in one direction₁And a reflected wavelength λ in the opposite direction₁The OTDR signal of (a). The optical circulator 520 may receive the wavelength λ₁And directs the reflected OTDR signal to wavelength coupler 530. Wavelength coupler 530 may couple wavelength λ₁Reflected OTDR signal and wavelength lambda of₂Can receive the wavelength lambda from wavelength decoupler 510, wavelength coupler 530 can combine the continuous optical signals of (a) wavelength lambda₂Of the optical signal. Wavelength coupler 530 may include a wavelength λ₁Reflected OTDR signal and wavelength lambda of₂The combined OTDR signal of the continuous optical signals is directed to amplifier 230 for transmission as output optical signal 550. Amplifier 230 may direct output signal 550 to modified OTDR instrument 245 (see fig. 2 and 3).

Although fig. 5 illustrates exemplary components of exemplary automatic fiber patch panel 255, in other embodiments, exemplary automatic fiber patch panel 255 may contain more, fewer, different, or otherwise configured components than those illustrated in fig. 5. In still other embodiments, one or more components of exemplary automatic fiber patch panel 255 may perform tasks described as being performed by one or more other components of exemplary automatic fiber patch panel 255. Moreover, one or more components of exemplary automatic fiber patch panel 255 may be located outside of exemplary automatic fiber patch panel 255, or the components may be distributed throughout the system described herein.

Fig. 6 is a flow diagram of an exemplary process 600 for locating a fault in the exemplary long haul fiber optic network 200. While the following description refers to exemplary modified OTDR instrument 245, this need not be the case when performing the operations included in exemplary process 600 in exemplary long haul network 200. In one implementation, one or more blocks of process 600 may be performed by a combination of devices and or components of exemplary long-range network 200.

The process of fig. 6 may begin with the detection of a failure in the exemplary long-haul network 200 (block 605). For example, assume that a fault has interfered with signal transmission. Assume further that the disturbance has triggered an automatic laser shutdown of the amplifier closest to the fault. For example, an automatic laser shutdown process may include a sequence in which each amplifier without an input signal or an output signal may be automatically shutdown. Thus, in this case, automatic laser shutdown allows locating the affected amplifier to be identified (block 610). The information related to the location of the affected amplifier may include the particular fiber line or link that includes the affected amplifier. For example, as shown in FIG. 2, a fault may be located on the exemplary long haul line 205.

An OTDR signal may be generated (block 615). In one embodiment, the OTDR signal may be an optical pulse, a series of optical pulses, and/or a continuous optical signal. For example, modified OTDR instrument 245 may generate wavelength λ₁To locate faults in the exemplary long haul network 200.

A continuous optical signal may be generated to energize an amplifier affected by an automatic laser shutdown (block 620). In the case of an automatic laser shutdown, although the OTDR may be transmitted through the affected (shutdown) amplifier, the automatic shutdown sequence may interfere with the OTDR signal before enough data is collected by the OTDR instrument to locate the fault. Thus, in one embodiment, exemplary modified OTDR instrument 245 may generate wavelength λ₂Of the optical signal. For example, wavelength λ₂May be of a particular signal strength and wavelength to prevent the exemplary amplifier from being energized230 and/or the automatic laser shutdown of the exemplary long-haul network 200. In this case, the wavelength λ₂May allow the OTDR signal generated at block 615 to pass through all amplifiers located between the modified OTDR instrument 245 and the fault in the long haul network 200.

At a wavelength λ₁Of the OTDR signal and wavelength lambda₂After all the continuous optical signals have been generated, the wavelength λ may be determined₂Continuous optical signal and wavelength lambda of₁The OTDR signals of (a) are combined (block 625). In one embodiment, as shown in fig. 3, modified OTDR instrument 245 may direct two signals to wavelength coupler 330 for transmission to the affected link. As long as the wavelength lambda₁Of the OTDR signal and wavelength lambda₂The successive optical signals of (a) are combined at block 625, and the exact order of blocks 615 and 620 may be unimportant.

The combined signal may be switched to the affected fiber link (block 630). For example, including the wavelength λ generated by the modified OTDR instrument 245₁Of the OTDR signal and wavelength lambda₂May be switched to a long-haul fiber line 205 in the exemplary long-haul network 200 shown in fig. 2. As shown in fig. 2, exemplary long-haul network 200 may include modified OTDR instruments 245 at either end of long-haul network 200. Thus, in this case, as will be in the examples described later, modified OTDR instrument 245 may direct the combined signal to either of long haul lines 205 or 210.

The continuous optical signal may be switched to a fiber link opposite the direction of the affected link (block 635). In one embodiment, exemplary automatic fiber patch panel 255 may couple a wavelength λ as described with respect to fig. 4 and 5₂To the optical fiber link in the opposite direction of the affected link. For example, once the combined signal has passed through the amplifier affected by the auto-off, the continuous signal may not be needed after the affected amplifier is exceeded. Thus, in such a case, automated fiber patch panel 255 mayThe continuous optical signal is switched to the opposite direction of the fiber link.

When the OTDR signal encounters a fault in the fibre network 200, said fault generates a reflected OTDR signal in the opposite direction to the transmitted OTDR signal. The reflected OTDR signal from the fault location may be switched to a fiber link in the opposite direction (block 640). In one embodiment, exemplary automatic fiber patch panel 255 may switch reflected OTDR signals to a fiber link in the opposite direction, as described with respect to fig. 4 and 5. For example, a reflected OTDR signal from a fault in the exemplary long haul fiber line 205 may be switched to the opposite direction long haul fiber line 210.

The reflected OTDR signal and the continuous optical signal on the opposite direction fiber link may be combined (block 645). In one embodiment, exemplary automatic fiber patch panel 255 may combine reflected OTDR signals and continuous optical signals on oppositely directed fiber links, as described with respect to fig. 4 and 5. For example, the automated fiber patch panel 255 may couple a wavelength λ from a fault on the exemplary long haul line 205₁Reflected OTDR signal and wavelength lambda of₂And the combined signal is transmitted over a long-haul fiber line 210 in the opposite direction to the long-haul line 205.

The reflected OTDR signal may be switched to an OTDR receiver (block 650). In one embodiment, the reflected OTDR signal may be switched by wavelength decoupler 340 to OTDR receiver 350 in modified OTDR instrument 245, as described with respect to fig. 3. For example, modified OTDR instrument 245 may receive a signal including wavelength λ₁Reflected OTDR signal and wavelength lambda of₂And wavelength decouplers 340 may combine the wavelengths lambda₁Is directed to OTDR receiver 350.

The continuous optical signal may be switched to an optical emptier (block 655). In one embodiment, the continuous optical signal may be switched by wavelength decoupler 340 to optical dump 360 in modified OTDR instrument 245, as described with respect to fig. 3. For exampleModified OTDR instrument 245 may receive signals including wavelength λ₁Reflected OTDR signal and wavelength lambda of₂And wavelength decouplers 340 may combine the wavelengths lambda₂Is directed to optical emptier 360.

The location of the fault may be determined based on the reflected OTDR signal. In one embodiment, modified OTDR instrument 245 may measure characteristics of a reflected OTDR signal and compare the characteristics with the transmitted OTDR signal to determine the distance to the fault that generated the reflection. For example, in modified OTDR instrument 245, OTDR receiver 350 and OTDR transmitter 310 may communicate information related to a reflected OTDR signal and a transmitted OTDR signal, respectively. In this case, central processing unit 370 may calculate the distance to the fault based on information from OTDR receiver 350 and OTDR transmitter 310.

By repeating process 600 from the opposite end of the affected fiber link, the location of the fault can be located with high accuracy.

The above description of the blocks included in FIG. 6 provides illustration and description, but is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. Although a series of blocks has been described with regard to the flowchart of fig. 6, the order of the blocks may be different in other implementations. For example, the generation of the OTDR signal and the generation of the continuous optical signal (blocks 615 and 620) may be performed in any order, or they may be performed simultaneously. Similarly, the switching of the continuous optical signal and the reflected OTDR signal to the opposite direction fiber link (blocks 635 and 640) may be performed in any order, or they may be performed simultaneously.

The process described with reference to fig. 6 may be further demonstrated by way of example. Fig. 7 is a diagram of an exemplary pair of signal paths in the exemplary long-range network 200 of fig. 2. As shown in fig. 7, modified OTDR instrument 245 may generate a wavelength λ₁Examples of (2)The linear OTDR signal 700 is thus used to remotely locate a fault 710 in the long haul network 200. Modified OTDR instrument 245 may be located at site 1. In one embodiment, site 1 may be located at one end of a long haul fiber optic line. In this case, site 1 may be a network operations center and one end of exemplary long haul lines 205 and 210. Modified OTDR instrument 245 may generate wavelength λ by the manner described in relation to fig. 3 and 6₁OTDR signal 700.

As shown in fig. 7, modified OTDR instrument 245 at site 1 may transmit OTDR signal 700 over long haul line 205 to amplifier 230 at site 2. Amplifier 230 at site 2 may have automatic fiber patch panels 255 located on the input and output sides of the exemplary amplifier 230. Automatic fiber patch panel 255 at site 2 may be configured as described with respect to fig. 4 and 5. In this case, automatic fiber patch panel 255 at site 2 may direct OTDR signal 700 to fault 710 on exemplary long haul line 205, as described with respect to fig. 4, 5, and 6.

As shown in fig. 7, fault 710 on long haul line 205 generates a reflection of OTDR signal 700, and reflected OTDR signal 700 may return to automatic fiber patch panel 255 at site 2. As described with respect to fig. 4, 5, and 6, automatic fiber patch panel 255 at site 2 may direct reflected OTDR signal 700 to exemplary long haul line 210 where reflected OTDR signal 700 may be received by modified OTDR instrument 245 at site 1. Modified OTDR instrument 245 at site 1 may process reflected OTDR signal 700 as described with respect to fig. 3 and 6.

As further shown in fig. 7, modified OTDR instrument 245 at site N may generate a second OTDR signal 700, which may be used to locate fault 710 in exemplary long haul network 200. Modified OTDR instrument 245 at site N may generate wavelength λ in the manner described with respect to fig. 3 and 6₁OTDR signal 700. Site N may be located at one end of long haul fiber optic lines 205 and 210. In this case, the location N may be a network operations center and an exemplary long-rangeOne end of lines 205 and 210.

As shown in fig. 7, modified OTDR instrument 245 at site N may transmit OTDR signal 700 over long haul line 210 to amplifier 230 at site 3. Amplifier 230 at site 3 may have automatic fiber patch panels 255 located on the input and output sides of the exemplary amplifier 230. Exemplary automatic fiber patch panels 255 may be configured as described with respect to fig. 4 and 5. Further, in this case, automatic fiber patch panel 255 at site 3 may direct OTDR signal 700 from amplifier 230 at site 3 on long haul line 210 to fault 710 on fiber line 205, which is the affected fiber link, as described with respect to fig. 4, 5, and 6.

As shown in fig. 7, fault 710 on long haul line 205 generates a reflection of OTDR signal 700, and reflected OTDR signal 700 may return to automatic fiber patch panel 255 at site 3. As described with respect to fig. 4, 5, and 6, automatic fiber patch panel 255 at site 3 may direct reflected OTDR signal 700 to line 205. In this case, automatic fiber patch panel 255 may direct OTDR signal 700 on long haul line 205 to modified OTDR instrument 245 at site N. Modified OTDR instrument 245 at site N may process reflected OTDR signal 700 as described with respect to fig. 3 and 6.

As also shown in fig. 7, exemplary OTDR signal 700 may pass through multiple amplifiers 230 between site N and site 3 on long haul line 210. Each amplifier 230 located between site N and site 3 may have automatic fiber patch panels 255 located on the input and output sides of the exemplary amplifier 230. In this case, automatic fiber patch panel 255 at each amplifier 230 on long haul line 210 may operate in a first or idle mode as described in fig. 4 and 5, thereby allowing exemplary OTDR signal 700 to pass through each amplifier 230 located between site N and site 3.

Fig. 8 is a diagram of another pair of exemplary signal paths in the exemplary long-range network of fig. 2. As shown in fig. 8, a modified OTDR instrument 245 may generate an exemplary continuous optical signal 800 that may be used to prevent automatic laser shutdown of the amplifier 230 closest to either side of the fault in the exemplary long haul network 200. For example, modified OTDR instrument 245 may generate continuous optical signal 800 at a particular signal strength and wavelength designed to prevent automatic laser shutdown of amplifier 230. In one embodiment, site 1 may be located at one end of the exemplary long haul route 205. In this case, site 1 may be a network operations center and one end of exemplary long haul lines 205 and 210. Modified OTDR instrument 245 may generate wavelength λ in the manner described with respect to fig. 3 and 6₂800 of the optical signal.

As shown in fig. 8, modified OTDR instrument 245 at site 1 may direct continuous optical signal 800 on exemplary long haul line 205 to exemplary amplifier 230 at site 2. Amplifier 230 at site 2 may have exemplary automatic fiber patch panels 255 located on the input and output sides of exemplary amplifier 230. Automatic fiber patch panel 255 may be configured as described with respect to fig. 4 and 5. In one embodiment, a fault 810 on the long haul line 205 may cause an automatic laser shutdown of the amplifier 230 at point 2 on the long haul line 205. In this case, with known signal strength and wavelength λ₂May allow transmission of an OTDR signal used to locate a fault 810, the known signal strength and wavelength λ₂Are designed to prevent automatic laser shut down of the amplifier 230.

Automatic fiber patch panel 255 at site 2 may direct continuous optical signal 800 from amplifier 230 on long-range line 205 to amplifier 230 on long-range line 210. Automatic fiber patch panel 255 at site 2 may process the continuous optical signal as described with respect to fig. 4, 5 and 6. As shown in fig. 8, continuous optical signal 800 may pass through long haul line 210 from amplifier 230 at site 2 to modified OTDR instrument 245 at site 1. Modified OTDR instrument 245 at site 1 may process continuous optical signal 800 as described in fig. 3 and 6.

As further shown in fig. 8, modified OTDR instrument 245 may generate a second exemplary continuous optical signal 800 at site N at a particular signal strength and wavelength designed to prevent automatic laser shutdown of amplifier 230 closest to either side of a fault in exemplary long haul network 200. Site N may be located at one end of exemplary long haul lines 205 and 210. In this case, site N may be the network operations center and one end of exemplary long haul lines 205 and 210. Modified OTDR instrument 245 at site N may generate wavelength λ in the manner described with respect to fig. 3 and 6₂800 of the optical signal.

As shown in fig. 8, modified OTDR instrument 245 at site N may direct continuous optical signal 800 on long haul line 210 to amplifier 230 at site 3 on long haul line 210. Amplifier 230 at site 3 may have exemplary automatic fiber patch panels 255 located on the input and output sides of amplifier 230. For example, exemplary automatic fiber patch panel 255 may be configured as described with respect to fig. 4 and 5. In one embodiment, a fault 810 on the long haul line 205 may cause an automatic laser shutdown of the amplifier at point 3 on the long haul line 205. In this case, with known signal strength and wavelength λ₂May allow transmission of an OTDR signal used to locate a fault 810, the known signal strength and wavelength λ₂Are designed to prevent automatic laser shut down of the amplifier 230. In this case, automatic fiber patch panel 255 at site 3 may direct continuous optical signal 800 from site 3 on long haul line 210 to amplifier 230 at site 3 on long haul line 205. The automated fiber patch panel 255 at site 3 may process the continuous optical signal 800 as described with respect to fig. 4, 5 and 6. As shown in fig. 8, continuous optical signal 800 may pass through long haul line 205 from amplifier 230 at site 3 to modified OTDR instrument 245 at site N. Modified OTDR instrument 245 at site 1 may process continuous optical signal 800 as described in fig. 3 and 6.

As also shown in fig. 8, the continuous optical signal 800 may pass through a plurality of amplifiers 230 between location N and location 3 on the long-haul line 210. In one embodiment, each amplifier 230 located between site N and site 3 may have automatic fiber patch panels 255 located on the input and output sides of the exemplary amplifier 230. In this case, the automatic fiber patch panel 255 at each amplifier 230 on the long haul line 210 may operate in a first or idle mode as described in fig. 4 and 5, thereby allowing a continuous optical signal 800 to pass through each amplifier 230 between site N and site 3.

Fig. 9 is a diagram of an exemplary configuration of a long-range network 200. As shown in fig. 9, the fault 910 may be located in the first interval of the exemplary long haul line 205 that is closest to the end points of the exemplary long haul lines 205 and 210. In the example shown in fig. 9, the location of modified OTDR instrument 245 relative to fault 910 may require conventional OTDR operation of modified OTDR instrument 245 at site 1. In this case, OTDR patch panel 920 may be installed at site 1. OTDR patch panel 920 may include an optical circulator 930. Optical circulator 930 may include any device capable of separating optical signals received from opposite directions in a single optical fiber. In one embodiment, the optical circulator 930 may receive a transmitted signal in one direction and a reflection of the same signal in the opposite direction. For example, the optical circulator 930 may receive the wavelength λ in a first direction₁And receives the wavelength lambda in the opposite direction₁The reflected OTDR signal of (a).

As shown in fig. 9, since no exemplary amplifier 230 is located in the signal path between exemplary modified OTDR instrument 245 and fault 910, a continuous signal generated at site 1 is not required to prevent automatic laser shutdown. In one embodiment, modified OTDR instrument 245 may generate an exemplary OTDR signal 940, as described with respect to fig. 3. For example, modified OTDR instrument 245 may generate wavelength λ₁Of the OTDR signal 940. In this case, the wavelength λ₁May be for performing optical time domain inversionKnown wavelength of radiation.

In one embodiment, modified OTDR instrument 245 at site 1 may direct OTDR signal 940 to optical circulator 930 in OTDR patch panel 250 and along long haul line 205 to fault 910. As shown in fig. 9, fault 910 generates a reflected OTDR signal 940 in the opposite direction of long haul line 205. Optical circulator 930 in OTDR patch panel 250 may receive reflected OTDR signal 940 and transmit reflected OTDR signal 940 to modified OTDR instrument 245 at site 1. Modified OTDR instrument 245 at site 1 may process reflected OTDR signal 940 as described with respect to fig. 3 and 6. In the configuration of the long haul network 200 shown in fig. 9, OTDR operations may be performed from site N as described with respect to fig. 6 and 7.

The foregoing description provides illustration and description, but is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention.

For example, certain exemplary components have been presented with respect to the automated fiber patch panel 250 of fig. 2, 4, 5, 6, and 7. These components are exemplary in nature and are used to help describe the functions such components can perform in conjunction with the fiber link fault locator system of the present invention. For example, the components described in fig. 2, 4, 5, 6 and 7 as circulators may be replaced by suitably configured power couplers.

Further, while the disclosed embodiments have been described as being suitable for use in long haul fiber optic networks, the systems and methods disclosed herein are applicable to any fiber optic line or link that includes multiple amplifier zones or short distances.

Specific terms like "fiber optic line" and "fiber optic link" have been referred to above. It should be understood that these terms are intended to be interchangeable. Also, terms referring to an amplifier (or amplifier station) and a repeater (or repeater station) are equivalent and refer to the same concept. Similarly, the terms relating to laser and continuous optical signals are equivalent and refer to the same concept. The terms "decoupler" and "splitter" are also equivalent and refer to the same concept.

The foregoing description provides examples and illustrations, but are not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention.

Even if specific combinations of features are cited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of the invention. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each dependent claim listed may refer directly to only one other claim, the disclosure of the present invention includes each dependent claim in combination with each other claim in the set of claims.

No element, act, or instruction used in the present application should be construed as critical or essential to the invention unless explicitly described as such. Also, as used herein, the article "a" is intended to include one or more items. Where only one item is intended, the term "one" or similar language is used. Further, the phrase "based on" is intended to mean "based, at least in part, on" unless explicitly stated otherwise.

Claims (13)

1. A system for locating a fault in a long haul fiber optic network, the system comprising:

a first apparatus configured to:

generating a first optical signal at a first wavelength;

generating a second optical signal at a second wavelength,

the second optical signal prevents automatic laser shutdown of at least one of the plurality of optical amplifiers along the first and second optical fiber links;

combining the first optical signal with the second optical signal to form a first combined signal; and is

Transmitting the first combined signal in a first direction over the first fiber optic link; a second apparatus configured to:

receiving the first combined signal from the first device;

separating the first combined signal to separate a first optical signal at the first wavelength from a second optical signal at the second wavelength;

transmitting the first optical signal to a target;

receiving a reflection of the first optical signal from the target as a first reflected optical signal;

combining the first reflected light signal from the target with the second light signal to form a second combined signal; and is

Transmitting the second combined signal to the first device in a second direction opposite the first direction over the second fiber optic link; and is

Wherein the first apparatus is further configured to:

receiving the second combined signal from the second apparatus;

separating the second combined signal to separate a first reflected optical signal at the first wavelength from a second optical signal at the second wavelength; and is

Determining a location of the fault based on the first reflected light signal.

2. The system of claim 1, wherein the target is a failure in a fiber link in the long haul fiber optic network.

3. The system of claim 1, wherein the second device comprises an optical circulator for transmitting the first optical signal and the first reflected optical signal.

4. The system of claim 1, wherein the second means comprises a power coupler for transmitting the first optical signal and the first reflected optical signal.

5. The system of claim 1, wherein the second means comprises a wavelength coupler and a wavelength decoupler for combining and separating at least one of:

the first optical signal and the second optical signal; or

The first reflected optical signal and the second optical signal.

6. A method for locating a fault in a long haul fiber optic network, the method comprising:

generating an optical time domain reflectometry signal;

transmitting the optical time domain reflectometry signal in a first direction over a first optical fiber path through at least one optical amplifier;

transmitting a continuous optical signal in the first direction over the first optical fiber path through the at least one optical amplifier,

wherein the continuous optical signal is transmitted in the first direction on the first optical fiber path through the at least one optical amplifier, and

wherein the continuous optical signal prevents an automatic laser shutdown of the at least one optical amplifier; and

receiving a reflection of the optical time domain reflectometry signal on the first optical fiber path in a second direction opposite the first direction;

transmitting the reflected optical time domain reflectometry signal in said second direction over a second optical fiber path,

wherein the second optical fiber path is not the first optical fiber path; and is

Determining a location of a fault on the first fiber path based on the reflected optical time domain reflectometry signal.

7. The method of claim 6, further comprising:

generating a second optical time domain reflectometry signal;

transmitting the second optical time domain reflectometry signal in the second direction over the second optical fiber path through at least one optical amplifier;

switching the second optical time domain reflectometry signal to the first optical fiber path in the second direction;

receiving a reflection of the second optical time domain reflectometry signal in the first direction over the first optical fiber path;

transmitting a reflected second optical time domain reflectometry signal in the first direction over the first optical fiber path; and is

Determining a location of a fault on the first fiber path based on the reflected second optical time domain reflectometry signal.

8. The method of claim 7, further comprising:

transmitting a second signal in the second direction on the second fiber path through the at least one optical amplifier.

9. The method of claim 8, wherein the second signal in the second direction on the second fiber path prevents an automatic laser shutdown of the at least one optical amplifier.

10. A system for locating a fault in a long haul fiber optic network, the system comprising:

a fiber optic network comprising a first fiber optic path and a second fiber optic path, wherein the first fiber optic path and the second fiber optic path each comprise at least one amplifier;

means for generating an optical time domain reflectometry signal at a first wavelength;

means for generating a continuous optical signal at a second wavelength;

means for combining the optical time domain reflectometry signal with the continuous optical signal to form a first combined signal;

means for transmitting the first combined signal in a first direction over the first fiber path through the at least one amplifier,

the continuous optical signal prevents the at least one optical fiber included on the first optical fiber path from being included

Automatic laser shut down of an amplifier;

means for switching a reflection of the optical time domain reflectometry signal from a second direction of the first optical fiber path opposite the first direction to a second direction of the second optical fiber path; and

means for determining a location of a fault on the first optical fiber path based on the reflected optical time domain reflectometry signal.

11. The system of claim 10, further comprising:

means for generating a second optical time domain reflectometry signal;

means for transmitting the second optical time domain reflectometry signal in the second direction over the second optical fiber path;

means for switching the second optical time domain reflectometry signal from the second direction of the second optical fiber path to the second direction of the first optical fiber path;

means for transmitting a reflection of the second optical time domain reflectometry signal in the first direction over the first optical fiber path; and

means for determining a location of a fault on the first optical fiber path based on the reflected second optical time domain reflectometry signal.

12. The system of claim 10, further comprising:

means for switching the continuous optical signal from the first optical fiber path in the first direction to the second optical fiber path in the second direction.

13. The system of claim 10, wherein the means for generating a continuous optical signal is a laser.