JP2009182030A - Optical amplifier and system, and excitation light beam monitoring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily monitor the state of an excitation light beam to be supplied to an amplifying medium of an optical amplifier. <P>SOLUTION: The optical amplifier (100) comprises the amplifying medium (10) which amplifies an optical signal by photoexcitation and outputs it, a light source unit (20) which outputs excitation light beams of a plurality of wavelengths for optically exciting the amplifying medium, an optical detection unit (40) which detects an excitation light beam having a specified wavelength among the plurality of wavelengths and switches the specified wavelength, and a waveguide unit (30) which supplies the excitation light beam from the light source unit to the amplifying medium through an optical fiber. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for monitoring laser light.

  In an amplifier of a relay system in optical communication, a laser that outputs pumping light for optical pumping is mounted on an amplification medium such as EDF (Erbium-Doped Fiber). As the excitation laser, for example, a laser diode (hereinafter referred to as “LD”) is used. In the optical amplifier, the front output of the LD is propagated through an optical fiber, and this is supplied to the amplification medium as pumping light.

  By the way, when an abnormality occurs in the pumping light in the optical amplifier, the optical signal to be relayed is not properly amplified. Therefore, in parallel with the amplification operation of the optical amplifier, it is monitored whether or not the state of the pumping light is normal.

As a method for monitoring the light from the laser, for example, a so-called back monitor is known which receives and analyzes the rear output light of a double-sided light emitting LD. A technique employing a back monitor is described in, for example, Patent Document 1 described later. The technique of this document uses the rear output value of the LD obtained by the back monitor to prevent the degradation and breakage of the LD due to the temperature change.
JP 2002-232073 A

  Since the back monitor monitors the rear output light of the LD, it is not suitable for monitoring the excitation light supplied to the amplification medium, that is, monitoring the front output light of the LD. In general, since laser light having a plurality of wavelengths is used as the excitation light, it is necessary to monitor the excitation light of each wavelength. However, it is difficult to construct a complicated and large-scale facility in an environment where installation of equipment is not easy, such as the seabed, or in a place where installation space is limited.

  The present invention has been made in view of the above problems, and an object thereof is to provide a technique for simply monitoring the state of excitation light to be supplied to an amplification medium.

  An optical amplifier according to the present invention includes an amplification medium that amplifies and outputs an optical signal by optical excitation, a light source unit that outputs excitation light of a plurality of wavelengths for optically exciting the amplification medium, and a plurality of wavelengths A light detection unit that detects excitation light of a specific wavelength and switches the specific wavelength; and a waveguide unit that supplies the excitation light from the light source unit to the amplification medium and the light detection unit through an optical fiber.

  The system according to the present invention includes the optical amplifier, a monitoring device connected to the optical amplifier, and a receiving terminal including a communication unit, and the monitoring device includes the optical amplifier related to the excitation light of the specific wavelength. A determination unit configured to determine the state of the excitation light using the detection result; and a transmission unit configured to transmit the determination result of the determination unit to the reception terminal.

  The pumping light monitoring method according to the present invention outputs pumping light having a plurality of wavelengths for optical pumping of an amplifying medium that amplifies and outputs an optical signal by optical pumping, branches the pumping light that is output, and partly by branching Is supplied to the amplifying medium, the excitation light having a specific wavelength among the other portions of the excitation light due to the branching is detected, and the specific wavelength is switched.

  According to the present invention, each of a plurality of wavelengths of excitation light can be easily monitored. This eliminates the need for constructing complicated and large-scale facilities, and makes it easy to monitor excitation light even in special environments such as the seabed or places where installation space is limited.

  FIG. 1 shows the configuration of the first embodiment of the present invention. In this embodiment, the present invention is applied to an optical amplifier of a relay system in optical communication. As shown in FIG. 1, the optical amplifier 100 includes an EDF 10 as an amplification medium provided in the communication line 11, a light source unit 20 that outputs excitation light for optically exciting the EDF 10, and excitation light from the light source unit 20. A waveguide unit 30 to be supplied to the EDF 10 and a light detection unit 40 for monitoring excitation light are provided.

  The EDF 10 amplifies and outputs an optical signal propagating in the direction indicated by the dotted arrow in the line 11 by the optical excitation effect caused by the incidence of the excitation light. The wavelength of the optical signal to be amplified can be, for example, a 1.5 μm band.

  The light source unit 20 includes an LD 20A that outputs excitation light having a wavelength λ1, and an LD 20B that outputs excitation light having a wavelength λ2. The laser beams output from the LD 20A and the LD 20B are lights having different wavelengths as shown in FIG. As the wavelengths λ1 and λ2, for example, 984 nm and 986 nm in the 0.98 μm band can be used.

  The waveguide unit 30 includes a multiplexer 31 and a multiplexer 32, and supplies the output 1 and the output 2 from the light source unit 20 to the EDF 10 and the light detection unit 40 through an optical fiber. As shown in FIG. 1, the multiplexer 31 multiplexes the output 1 and the output 2 and divides them into excitation light 3 to the EDF 10 and branched light 4 to the light detection unit 40. The multiplexer 32 makes the excitation light 3 from the multiplexer 31 incident on the EDF 10. In the configuration shown in FIG. 1, the pumping light 3 is supplied to the EDF 10 by the forward pumping method. Alternatively, the pumping method of the EDF 10 may be the backward pumping.

  The light detection unit 40 includes a filter (FIL: Filter) 41A and a light receiver (PD: Photo Detector). The filter 41A transmits one wavelength to be monitored among the wavelengths λ1 and λ2 of the light source unit 20, and switches the wavelength to be transmitted periodically or arbitrarily. The light receiver 42 detects the transmitted light 5 from the filter 41A.

  A series of operations of the optical amplifier 100 configured as described above will be described. First, the multiplexer 31 multiplexes the output 1 (λ1) and the output 2 (λ2) from the light source unit 20. Thereafter, the multiplexer 31 divides the combined light into the excitation light 3 and the branched light 4. The multiplexer 32 makes the excitation light 3 from the multiplexer 31 incident on the EDF 10. When the branched light 4 from the multiplexer 31 is incident, the filter 41A outputs only the light having the transmission wavelength (λ1 or λ2) at that time as the transmitted light 5. The light receiver 42 detects the transmitted light 5 from the filter 41A.

  Assume that the wavelength to be monitored, that is, the transmission wavelength of the filter 41A is λ1. At this time, if the transmitted light 5 of λ1 is not detected by the light receiver 42, it means that some abnormality has occurred with respect to λ1, such as the output fiber of the LD20A (λ1) being disconnected, or the LD20A itself is defective. I can know. Further, when the transmitted light 5 of λ1 is properly detected by the light receiver 42, it can be recognized that there is no abnormality with respect to λ1. Then, by switching the transmission wavelength of the filter 41A from λ1 to λ2, λ2 can be monitored in the same manner as described above.

  As described above, according to this embodiment, it is possible to easily monitor each of the excitation lights having a plurality of wavelengths. Since this embodiment does not require the construction of a complicated and large-scale system, it is suitable for a special environment such as the seabed or a place where installation space is limited.

  In addition, since the present embodiment directly monitors the forward output light actually used as the excitation light, not the rear output light of the LD, it is possible to detect a situation where the power of the excitation light is reduced due to fiber breakage or the like. . Furthermore, in the case of an optical amplifier in which a reflector such as a fiber grating is provided on the laser output side for an external resonator, it is possible to detect multimode excitation light due to abnormality of the reflector.

  FIG. 3 shows the configuration of the second embodiment of the present invention. The optical amplifier 200 of the present embodiment reduces light having a wavelength that is not monitored by the light detection unit 40 to the EDF 10 as excitation light in addition to the excitation light 3 from the light source unit 20.

  As a configuration for this, as shown in FIG. 3, the light detection unit 40 includes a reflector 41B (REF: Reflector) instead of the filter 41A (FIG. 1) in the above-described embodiment. Whereas the filter 41A described above is responsible only for transmission, the reflector 41B of the present embodiment transmits one of the wavelengths λ1 and λ2 of the light source unit 20 and reflects the light of the other wavelength. Is. Further, similarly to the filter 41A, the reflector 41B switches the transmission wavelength to be monitored periodically or arbitrarily. The reflector 41B transmits the transmitted light 5 to the light receiver. The light receiver 42 detects the transmitted light 5. In addition, the reflector 41B reflects the reflected light 6 that is not monitored, and returns it to the waveguide unit 30.

  The waveguide unit 30 includes a duplexer 33, a multiplexer 34, and an isolator 35 in addition to the configuration in the above-described embodiment (FIG. 1). The duplexer 33 makes the branched light 4 from the light source unit 20 incident on the reflector 41B, and guides the reflected light 6 returned from the reflector 41B to the multiplexer. Further, an isolator 35 is inserted between the duplexer 33 and the multiplexer 31 in order to prevent the reflected light 6 from returning to the light source unit 20. The multiplexer 34 enters the EDF 10 using the reflected light 6 from the duplexer 33 as excitation light.

  In the configuration of FIG. 3, the excitation method of the EDF 10 is bidirectional excitation in which forward excitation by the excitation light 3 from the multiplexer 32 and backward excitation by the reflected light 6 from the multiplexer 34 are combined. With this method, interference between the excitation light 3 and the reflected light 6 incident on the EDF 10 can be avoided.

  Note that the configuration of the present embodiment may be a configuration of only forward excitation or a configuration of only backward excitation, instead of the above-described bidirectional excitation configuration. As an example, FIG. 4 shows a configuration in which only forward excitation is applied. In this case, a multiplexer 36 for supplying the reflected light 6 to the EDF 10 by forward pumping is disposed in the waveguide 30 of the optical amplifier 201 instead of the multiplexer 34 in FIG. Thereby, the reflected light 6 from the multiplexer 36 and the excitation light 3 from the multiplexer 32 are both incident on the EDF 10 by forward excitation.

  Each of the configurations of FIGS. 3 and 4 supplies the reflected light 6 that is not monitored among the excitation light and the excitation light 3 from the light source unit 20 to the EDF 10 of the same line 11. Alternatively, the excitation light 3 and the reflected light 6 may be supplied to the EDFs of different communication lines. A configuration example in that case is shown in FIG.

  The optical amplifier 202 shown in FIG. 5 supplies pumping light to the EDF 10A and the EDF 10B in the two lines 11A and 11B that are opposite lines. The waveguide unit 30 of the optical amplifier 202 is provided with a multiplexer 37 on the line 11B side. In such a configuration, the pumping light 3 from the light source unit 20 pumps forward the EDF 10A of the line 11A in the same manner as in the embodiment shown in FIG. On the other hand, the reflected light 6 from the reflector 41B is guided to the multiplexer 37 by the duplexer 33, and backwardly excites the EDF 10B on the opposite line 11B side.

  According to the above aspect, since the excitation light is supplied to the opposite line, the optical signal on the opposite line can be amplified.

  The excitation method on the line 11B side where the reflected light 6 is incident is not limited to the above-described backward excitation, but may be forward excitation. The form is shown in FIG. The waveguide unit 30 of the optical amplifier 203 shown in FIG. 6 includes a multiplexer 38 for exciting the EDF 10B forward with the reflected light 6 instead of the multiplexer 37 of FIG.

  As described above, according to this embodiment, similarly to the above-described embodiment, excitation light having a plurality of wavelengths can be easily monitored. In addition, among the excitation light once branched for monitoring, light that is not to be monitored is reduced to the EDF 10, so that the output from the light source unit 20 can be used effectively.

  FIG. 7 shows the configuration of the third embodiment of the present invention. This embodiment is a system for externally monitoring the state of excitation light used in the optical amplifier according to the present invention. The system 300 includes a monitoring device 50 connected to the light detection unit 40 of any of the optical amplifiers (100, 200, 201, 202, 203) described above, and a receiving terminal 60 having a wireless or wired communication function. The monitoring device 50 is not limited to being configured as a device separate from the optical amplifier, and may be configured as part of the optical amplifier.

  The monitoring device 50 includes a determination unit 51 and a transmission unit 52 as shown in FIG. The determination unit 51 determines the state of the excitation light to be monitored based on the transmission wavelength of the filter 41A (or the reflector 41B) at the current time and the detection result of the light receiver. The transmission unit 52 notifies the reception terminal 60 of the determination result of the determination unit 51 by wireless communication or wired communication.

  With reference to FIG. 7, the example of determination by the determination part 51 is demonstrated. Here, as an example, it is assumed that the monitoring target is excitation light of wavelength λ1. The determination unit 51 compares the voltage value P1 detected by the light receiver 42 with respect to λ1 with a voltage value Pt (≧ 0) of a predetermined determination threshold value. If the detection value (P1) exceeds the threshold value (Pt) as a result of the comparison, it is considered that an appropriate amount of λ1 has been detected, and it is determined that the excitation light of λ1 is normal (“determination case 1”).

  On the other hand, if the detected value (P1) is less than or equal to the threshold value (Pt), it is considered that λ1 is not detected in an appropriate state, and it is determined that an abnormality has occurred in λ1 (“determination case 2”). Thereafter, when the transmission wavelength of the filter 41A (or the reflector 41B) is switched from λ1 to λ2, the determination unit 51 determines this λ2 in the same procedure as described above.

  The transmitting unit 52 transmits the determination result of the determining unit 51 to the receiving terminal 60. The receiving terminal 60 receives the determination result and displays it on the screen. Thereby, the manager who has viewed the receiving terminal 60 can grasp the state of the excitation light of each wavelength.

  Note that the form of determination is not limited to two stages of normal / abnormal as described above, and the state of excitation light such as normal / caution / warning may be determined in three or more stages. In that case, a plurality of threshold values (Pt) are set according to the number of stages.

  As in the third embodiment, by providing the monitoring device 50 or the receiving terminal 60, it is possible to quickly grasp a failure from a remote location. As a result, the failure recovery operation can also be performed quickly.

  In practicing the present invention, the wavelength and number of pumping light and the wavelength of the optical signal to be amplified are not limited to those in the above embodiments. The excitation method of the amplification medium is not limited to the illustrated one, and any method suitable for the communication quality required for the communication line can be adopted.

  The amplification medium is not limited to the EDF (10) as in each of the above embodiments, and may be other rare earth-doped fibers such as thulium-doped fiber or praseodymium-doped fiber. . Further, the present invention is not limited to the form using the rare earth-doped fiber, but can be applied to, for example, an amplifier using the Raman effect.

  The multiplexer (31, 32, 34, 36, 37, 38) and the demultiplexer (33) are not limited to a device that handles only multiplexing or demultiplexing, but a device that functions as a multiplexer / demultiplexer Also good. Moreover, in order to fulfill | perform the function calculated | required by each, each may be comprised by one device, or may be comprised by multiple.

1 is a configuration diagram of an optical amplifier according to a first embodiment of the present invention. It is explanatory drawing regarding the wavelength of the excitation light in embodiment of this invention. It is a block diagram of the optical amplifier which concerns on the 2nd Embodiment of this invention. It is a block diagram of the modification of the optical amplifier which concerns on the 2nd Embodiment of this invention. It is a block diagram of the modification of the optical amplifier which concerns on the 2nd Embodiment of this invention. It is a block diagram of the modification of the optical amplifier which concerns on the 2nd Embodiment of this invention. It is a block diagram of the system which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

100,200,201,202,203: Optical amplifier
300: System
10: EDF, 11: Communication line
20: Light source, 20A, 20B: LD
30: Waveguide, 31,32,34,36,37,38: Multiplexer, 33: Demultiplexer, 35: Isolator (ISO)
40: Photodetector, 41A: Filter (FIL), 41B: Reflector (REF), 42: Receiver (PD)
50: monitoring device, 51: determination unit, 52: transmission unit
60: Receiving terminal
1, 2: Output, 3: Excitation light, 4: Branch light, 5: Transmitted light, 6: Reflected light

Claims (16)

An amplification medium that amplifies and outputs an optical signal by optical excitation;
A light source unit that outputs excitation light of a plurality of wavelengths for optically exciting the amplification medium;
A light detection unit that detects excitation light of a specific wavelength of the plurality of wavelengths and switches the specific wavelength; and
An optical amplifier comprising: a waveguide unit that supplies excitation light from the light source unit to the amplification medium and the light detection unit through an optical fiber. The light detection unit returns the excitation light having a wavelength different from the specific wavelength among the excitation light supplied by the waveguide unit to the waveguide unit,
The optical amplifier according to claim 1, wherein the waveguide unit supplies excitation light from the light detection unit to the amplification medium. The amplification medium is provided in each of a plurality of communication lines,
3. The optical amplifier according to claim 2, wherein the waveguide unit supplies excitation light from the light source unit and excitation light from the light detection unit to amplification media of different communication lines.   4. The optical amplifier according to claim 2, wherein the waveguide section supplies the excitation light from the light detection section to the amplification medium by backward excitation.   5. The optical amplifier according to claim 1, wherein the waveguide unit supplies pumping light from the light source unit to the amplification medium by forward pumping. 6.   The optical amplifier according to claim 1, wherein the light detection unit includes a filter that selectively transmits excitation light from the waveguide unit, and a photodetector that detects light transmitted through the filter.   The light detecting unit selectively transmits excitation light from the waveguide unit and reflects excitation light having a wavelength different from the wavelength of the transmitted light, and light detection for detecting the transmitted light of the reflector 6. The optical amplifier according to claim 2, further comprising: An optical amplifier according to any one of claims 1 to 7, a monitoring device connected to the optical amplifier, and a receiving terminal including a communication unit,
The monitoring apparatus includes: a determination unit that determines a state of the excitation light using a detection result of the optical amplifier related to the excitation light of the specific wavelength; and a transmission unit that transmits the determination result of the determination unit to the reception terminal. A system characterized by comprising.   The determination unit determines that the excitation light of the specific wavelength is normal when a voltage value of the detection result exceeds a threshold value, and that the excitation light is abnormal when the voltage value is equal to or less than the threshold value. The system of claim 8, wherein the system is determined. Outputs excitation light of multiple wavelengths for optical excitation of an amplification medium that amplifies and outputs an optical signal by optical excitation,
Branching the output excitation light and supplying a part of the excitation light from the branch to the amplification medium;
An excitation light monitoring method characterized by detecting excitation light of a specific wavelength among excitation light of other parts due to the branching and switching the specific wavelength.   The pumping light monitoring method according to claim 10, wherein pumping light having a wavelength different from the specific wavelength is supplied to the amplification medium among pumping light at other portions due to the branching. Providing the amplification medium in each of a plurality of communication lines;
Supplying a part of the excitation light branched from the output excitation light and the excitation light having a wavelength different from the specific wavelength among the other parts of the excitation light due to the branching to amplification media of different communication lines The excitation light monitoring method according to claim 11.   The excitation light monitoring method according to claim 11 or 12, wherein excitation light having a wavelength different from the specific wavelength and to be supplied to the amplification medium is supplied to the amplification medium by backward excitation.   The excitation light monitoring method according to any one of claims 10 to 13, wherein the part of the excitation light that is branched from the output excitation light and supplied to the amplification medium is supplied by forward excitation.   The excitation light according to any one of claims 10 to 14, further comprising: determining a state of the excitation light using a detection result relating to the excitation light of the specific wavelength, and transmitting the determination result. How to monitor.   In the determination, when the voltage value of the detection result exceeds a threshold value, it is determined that the excitation light of the specific wavelength is normal, and when the voltage value is equal to or less than the threshold value, the excitation light is determined to be abnormal. The excitation light monitoring method according to claim 15, wherein:

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