CN101841746A - Wavelength division multiplexing passive optical network optical line terminal having shared protection function - Google Patents

Abstract

The invention discloses a wavelength division multiplexing passive optical network optical line terminal with a shared protection function. The optical line terminal is provided with two ports on the outside, which are respectively called the main port and the standby port. Module, backup optical transceiver module and control module, the main optical transceiver module is connected to the main port, the backup optical transceiver module is connected to the standby port, the control module is connected to the main optical transceiver module and the backup optical transceiver module; the backup optical transceiver module is at least partially optical The light source of the unit adopts a wavelength adjustable light source. The optical line terminal provided by the present invention can realize the protection of all wavelength optical transceivers in the optical line terminal of the wavelength division multiplexing passive optical network at the cost of small redundant components, and when used in a network with dual-fiber backup, it can Realize the fault protection switching of the feeder optical fiber and the partial recovery of the partial fault of the distribution optical fiber, and even realize the recovery of multiple concurrent faults in the network.

Description

A wavelength division multiplexing passive optical network optical line terminal with shared protection function

technical field

The invention relates to a passive optical network, in particular to an optical line terminal of a wavelength division multiplexing passive optical network.

Background technique

Optical fiber access technology is one of the main technologies to realize the next-generation broadband access network. It has the characteristics of high bandwidth, large capacity, high reliability, and good service quality, and it is convenient to realize multi-network integration of voice, data, and video. With the increase of service types and bandwidth carried by the access network, especially the possible incorporation of voice services, the requirements for its reliability are getting higher and higher, which is specifically reflected in the improvement of network survivability requirements, that is, The network is required to have redundant protection and fast recovery capabilities in the event of failure, and it should be able to maintain communication to the maximum extent even in the event of a catastrophic accident. From the perspective of network cost, such protection should be realized at a small cost.

In the passive optical network (hereinafter referred to as PON) technology, there are currently two technologies: wavelength division multiplexing passive optical network (hereinafter referred to as WDM-PON) and time division multiplexing passive optical network (hereinafter referred to as TDM-PON). TDM-PON technology is relatively mature, with high bandwidth utilization rate and relatively low device cost, and has been widely used; while WDM-PON can provide higher bandwidth for each access terminal and has good scalability, which can be used for future It can be said that it is the development trend of the future optical access network to provide guarantee for network application upgrade and expansion. However, the cost of its components is relatively high, and the utilization rate of optical bandwidth resources is relatively low. However, various low-cost multi-wavelength light source solutions It is proposed that the practical application of WDM-PON has become possible. In addition, whether it is TDM-PON technology or WDM-PON technology, the maximum number of users that can be accessed is limited by power and bandwidth, which still has restrictions on the application of some high-density access occasions. It is still difficult to realize real fiber-to-the-home or fiber-to-the-desktop by simply using TDM-PON or WDM-PON technology in urban communities, high-rise buildings, companies, and colleges. In contrast, the mixed use of TDM-PON and WDM-PON technology can achieve as many as hundreds or even thousands of user access numbers under the premise of guaranteed bandwidth, with higher bandwidth resource utilization and higher cost performance , and can provide a smooth transition for the upgrade process from TDM-PON to WDM-PON.

Optical access network mainly consists of optical line terminal (hereinafter referred to as OLT), optical fiber distribution network (hereinafter referred to as OND) and corresponding link nodes (usually including a remote node (hereinafter referred to as RN)) and optical network unit (hereinafter referred to as ONU) /Optical network terminal (hereinafter referred to as ONT) consists of several parts, and the redundant protection of the optical access network can also be carried out separately for these parts, because the failure of the optical backbone/feeder fiber part in the OLT and optical fiber distribution network will affect the network Access to all users in the network, so it is usually the first place to be considered when considering network protection. In addition to the protection of the optical fiber part, in addition to using double optical fibers or even independent routes, there is usually an OLT or ONU end that provides monitoring and switching functions to cooperate with the protection and restoration of the optical fiber link. Therefore, the OLT with protection function is The key to enabling network protection and recovery.

At present, the protection of OLT in TDM-PON can be realized by double optical transceiver modules or double OLT, because there is only one pair of optical transceiver modules in OLT, so even if double redundancy is used, the cost increase is still relatively large compared to the entire network. It is not significant, but if the protection of OLT in WDM-PON also adopts double redundancy, the increased cost will become the main limitation of the realization of this scheme, and its protection efficiency is also too low. At present, WDM-PON uses mutual backup of OLTs of different PONs to protect against fiber failures, provides switching functions in OLT or ONU to protect redundant optical fiber paths, and uses redundant light sources in OLTs For other fixed-wavelength light sources in the OLT, a solution that can protect both the optical transceiver in the OLT and the fault of the optical fiber has not yet been seen.

Contents of the invention

Purpose of the invention: In order to overcome the limitations of PON protection in the prior art, the present invention provides a kind of OLT with shared protection function suitable for WDM-PON, which can provide flexible and more for comprehensive protection.

Technical scheme: in order to achieve the above object, the technical scheme adopted in the present invention is:

A wavelength division multiplexing passive optical network optical line terminal with a shared protection function, which is provided with two external ports, which are respectively called the main port and the standby port, and the number of uplink/downlink working wavelengths of the main port is m , the number of uplink/downlink working wavelengths of the backup port is n, which includes the main optical transceiver module, the backup optical transceiver module, and the control module. The two ports can work independently of each other, back up each other, or simultaneously through the following connection methods function of work. The main optical transceiver module sends downlink signals with a wavelength of λ ₁ ~ λ _m , receives uplink signals with a wavelength of λ ₁ ' ~ λ _m ', and connects to the main port; the standby optical transceiver module includes one or more optical transceiver units, and transmits wavelengths of The downlink signal of Λ ₁ ~ Λ _n and the uplink signal of receiving wavelength Λ ₁ ' ~ Λ _n ' are connected to the standby port, and the (adjustable) wavelength range of the optical transceiver unit must at least cover all the wavelengths that need to be protected on the main port range, the (tunable) wavelength range of the light source may also be in the wavelength range where the transmission wavelength range of the main port to be protected is shifted by a non-zero integer multiple of the free spectrum interval (hereinafter referred to as FSR) of the remote node, The light source of all or part of the optical transceiver unit adopts wavelength-tunable light source; Connect with the control terminal of the standby optical transceiver module. The OLT in this connection mode is called the master-standby OLT.

The OLT may also include a 2×2 (g×h means having g input ports and h output ports, or having h input ports and g output ports) optical path switching modules for optical path selection and switching, so The main optical transceiver module and the standby optical transceiver module are respectively connected to the main port and the standby port through the 2×2 optical path switching module, and the control module also controls the switching of the 2×2 optical path switching module, and the control of the connection to the 2×2 optical path switching module end. The OLT in this connection mode is called the main-standby-switching OLT.

The main optical transceiver module can adopt the structure of the optical transceiver module in the OLT of various existing WDM-PONs, such as adopting a Fabry-Perot laser array (hereinafter referred to as FP-LD array), arrayed waveguide grating (hereinafter referred to as AWG for short) and a broadband light source composed of an optical transceiver array structure, can also adopt a fixed-wavelength light source structure with a transmission wavelength of λ ₁ ~ λ _m at a lower cost than an adjustable light source, and use a multiplexer to combine all transmitted The wavelengths are multiplexed into one optical fiber, similarly using a demultiplexer to receive the downlink signals with the wavelengths λ ₁ '~λ _m ' into each optical detector. Here, the uplink/downlink signals can be combined inside the optical transceiver unit, or can be combined at the output/input end of the multiplexer/demultiplexer with an optical circulator or a broadband multiplexer.

The number of optical transceiver units of the above-mentioned standby optical transceiver module can be no greater than the number of optical transceiver units to be protected in the main optical transceiver module, and the transceiver signals of the optical transceiver units are combined by couplers or optical circulators (according to the upper/lower The relationship between wavelengths Λ _i ' and Λ _i , n≥i≥1, is used to select a wavelength-independent coupler or a wavelength-dependent coupler, also known as a broadband multiplexer/combiner). When n=1, OLT has the highest protection efficiency, and it is recommended to use when the failure rate of OLT and optical fiber link in the network is very low; when n>1, it is necessary to use combiner or optical switch and multiplexer to connect Multiple signals are combined into one and connected to the spare port; in the case that n light sources are all adjustable light sources, it is necessary to use n×m optical switches to connect these optical transceiver units to the m input ports of the multiplexer. When n' fixed-wavelength light sources are used in the optical transceiver module, an (n-n')×m optical switch is used to connect the adjustable optical transceiver unit to m input ports of the multiplexer. When n=1, or when using a combiner to combine multiple signals into one when n>1, a wavelength-tunable optical detector is required, and its bandwidth is smaller than the channel interval. The wavelength adjustment range of the wavelength tunable light source should cover the wavelength range occupied by all the transmission wavelengths that need to be protected on the main port, or cover the wavelength range where the transmission wavelength range is shifted by a non-zero integer multiple of the FSR of the remote node , the wavelength adjustment range of the wavelength-tunable photodetector should cover the wavelength range occupied by all receiving wavelengths to be protected at the main port; the wavelength-tunable photodetector can be composed of a broadband photodetector and a tunable filter.

Beneficial effects: the OLT provided by the present invention can improve the protection efficiency of WDM-PON by adopting the shared protection technology, especially when the number of optical transceiver units in the standby optical transceiver module is n=1, the OLT can be realized with the minimum redundancy. The protection of all working wavelength optical transceiver units in the network; when using the OLT provided by the present invention under the situation of dual-fiber backup in the network, it can also restore the trunk/feeder fiber and distribution fiber failures, and can be used for some local failures of distribution fibers. Partial recovery can be achieved without affecting other normal working ONUs, and recovery of multiple concurrent faults in the network can be realized; the use of a unified optical transceiver unit design in the standby optical transceiver module can reduce the type and quantity of spare devices required by the OLT , while reducing the complexity of the OLT's internal assembly and its connection with external devices.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a schematic structural diagram of the main optical transceiver module;

Fig. 3 is a schematic structural diagram of a standby optical transceiver module;

Fig. 4 is a schematic diagram of recovery of the WDM-PON network using the OLT provided by the present invention under several network failure situations.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

Description of letters and symbols in graphics:

As shown in Figure 1, there are two kinds of OLTs for WDM-PON with shared protection functions, and there are main ports and standby ports outside. The number of uplink/downlink working wavelengths to be protected for the main port is m (here, all wavelengths need to be protected as an example), which are respectively recorded as λ ₁ '～λ _m ' and λ ₁ ～λ _m , where m>1; The number of uplink/downlink working wavelengths of the port is n, which are respectively marked as Λ ₁ '～Λ _n ' and Λ ₁ ～Λ _n , where m≥n≥1, which pass through the The connection method realizes the function that the two ports can work independently of each other, back up each other, or work at the same time. As shown in Figure 1(a), the main-standby OLT includes the main optical transceiver module, the backup optical transceiver module and the control module, wherein the main optical transceiver module sends downlink signals with a wavelength of λ ₁ ~ λ _m , and receives a wavelength of λ ₁ The uplink signal of '～λ _m ' is connected to the main optical fiber through the main port; the standby optical transceiver module includes one or more optical transceiver units, and the light source of all or part of the optical transceiver units adopts a wavelength-tunable light source, and its transmission wavelength is Λ ₁ to Λ _n downlink signals, receive uplink signals with wavelengths of Λ ₁ '～Λ _n ', and connect the backup optical fiber through the backup port; the control module is connected to the control port of the main optical transceiver module and the backup optical transceiver module, and controls the main optical transceiver module Transmit and receive with the standby optical transceiver module. Figure 1(b) is the master-standby switching OLT. Compared with the structure in Figure 1(a), a 2×2 optical switch used as a 2×2 optical path switching module is added for optical path selection and switching. control module.

FIG. 2 is a schematic diagram of three structures of the main optical transceiver module in the structure of FIG. 1 . Figure 2(a) uses fixed-wavelength optical transceivers with transmit wavelengths λ ₁ ~ λ _m and receive wavelengths λ ₁ ' ~ λ _m ', and uses a multiplexer/demultiplexer to combine all downlink signals with uplink Signals are multiplexed and demultiplexed. Figure 2(b) uses a structure in which the light source and the photodetector are separated, and the up/down optical signals are combined at the output/input end of the multiplexer/demultiplexer through an optical circulator, while Figure 2(c) is The add/drop optical signals are combined at the output/input end of the multiplexer/demultiplexer through a broadband multiplexer.

FIG. 3 is a schematic diagram of three structures of the standby optical transceiver module in the structure of FIG. 1 . Figure 3(a) shows the simplest structure of the standby transceiver module, which consists of a wavelength-tunable light source (with an isolator) and a wavelength-tunable photodetector to combine the transceiver signals through a coupler (or optical circulator). The wavelength tunable light source is composed of a wavelength tunable laser, the wavelength tunable photodetector is composed of a tunable filter and a photodetector, and the coupler can To choose; the OLT using the backup optical transceiver module of this structure has the highest protection efficiency, and it is recommended to use it when the failure rate of the OLT and the optical fiber link is very low. The wavelength adjustment range of the wavelength tunable light source should cover the wavelength range occupied by all the transmission wavelengths that need to be protected on the main port, or cover the wavelength range where the transmission wavelength range is shifted by a non-zero integer multiple of the FSR of the remote node , the wavelength adjustment range of the wavelength-tunable photodetector should cover the wavelength range occupied by all receiving wavelengths that need to be protected at the main port. Figure 3(b) is a structure when there are optical transceiver units with n wavelengths in the standby optical transceiver module, which uses an n×m optical switch to connect n optical transceiver unit ports to m input ports of the multiplexer , and combine multiple signals into one and connect to the spare port. Fig. 3(c) is another structure when there are optical transceiver units with n wavelengths in the standby optical transceiver module, which uses a combiner to combine multiple signals, and this structure can be adopted when the value of n is small.

Fig. 4 is the situation that the WDM-PON network using the OLT provided by the present invention realizes recovery under several network failure situations, wherein the solid line is an optical fiber that can communicate normally, and the dotted line is an optical fiber with a break point that cannot communicate normally. Figure 4(a) is the recovery situation when the network is partially faulty. When an individual optical transceiver unit fails in the main optical transceiver module of the OLT or/and the distribution fiber of the corresponding ONU connected to it fails, the optical transceiver module of the backup optical transceiver module can be used. The transceiver unit sends and receives the signal of the corresponding faulty wavelength to realize recovery; as shown in Figure 4 (a), when TRx ₂ or/and its corresponding upstream and downstream operating wavelengths are λ ₂ ' and λ ₂ ONUs in the main optical transceiver module of the OLT ₂ When the connected distribution fiber breaks down, the standby optical transceiver module (the simplest structure of a single optical transceiver unit is used here) realizes the restoration of network functions by sending and receiving signals with wavelengths of λ ₂ ' and λ ₂ ; using this structure When the OLT restores this local fault, it may not affect other wavelengths (downlink signals λ ₁ , λ ₃ ...λ _m in this example, uplink signals λ ₁ ', λ ₃ '...λ _m ') normal work. Figure 4(b) shows the network recovery situation in the case of a feeder fiber failure. Taking the main-standby-switching OLT as an example, after the switching of the 2×2 optical path switching module, the signal in the main optical transceiver module can be transmitted through the backup fiber link Communicate with each ONU. Figure 4(c) shows the recovery situation in the case of multiple faults in the distributed optical fiber. Taking the OLT with the main-standby-switching structure as an example, a standby optical transceiver module with only one optical transceiver unit is used. As shown in the figure, when connected When both the main distribution fiber of ONU ₁ and ONU ₂ and the backup distribution fiber connected to ONU _m fail, the OLT can switch the downlink wavelength λ ₁ ... λ _m-1 and the uplink wavelength to The signals of λ ₁ '...λ _m-1 ' are switched to the standby optical fiber for transmission, and the standby transceiver module is used to send and receive λ _m ', λ _m wavelength signals to communicate with ONU _m through the main distribution optical fiber to realize the restoration of the entire network; similar When the backup optical transceiver module with n optical transceiver units is used in the OLT, at least 2n+1 local faults including the failure of the optical transceiver unit of the main optical transceiver module and the single fiber fault of the distribution fiber in the network can be realized full recovery. Fig. 4 (d) shows the recovery situation when OLT provided by the present invention is used in the network with ring topology when there is an optical fiber link failure on the ring, when the optical fiber link connecting ONU ₁₁ and ONU ₁₂ is connected on the ring When a fiber break occurs, if the two ONUs both use the add/drop wavelength λ ₁ '/λ ₁ , in TDM/WDM-PON, the two ports of the OLT can be used to simultaneously transmit and receive λ ₁ ' and λ ₁ to realize the affected The service of the ONU ₁₂ is restored.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also possible. It should be regarded as the protection scope of the present invention.

Claims (9)

1. Wavelength division multiplexing passive optical network optical line terminal with share protect function, it is characterized in that: described optical line terminal outside is provided with two ports, be called main port and standby port, inside comprises and can work independent of one another, backup mutually, the key light transceiver module that also can work simultaneously and standby optical transceiver module, and receive from the feedback signal of key light transceiver module and standby optical transceiver module and control the control module of the transmitting-receiving of key light transceiver module and standby optical transceiver module, described key light transceiver module connects main port, standby optical transceiver module connects standby port, and control module is connected with the control end of key light transceiver module and standby optical transceiver module respectively; Described standby optical transceiver module comprises one or more smooth Transmit-Receive Units, and the light source of all or part of smooth Transmit-Receive Unit adopts Wavelength tunable light source.

2. the Wavelength division multiplexing passive optical network optical line terminal with share protect function according to claim 1; it is characterized in that: described optical line terminal comprises that also is used for 2 * 2 optical path switching modules that light path is selected and switched; described key light transceiver module is connected main port and standby port with standby optical transceiver module respectively by 2 * 2 optical path switching modules, and described control module also is connected with the control end of 2 * 2 optical path switching modules.

3. the Wavelength division multiplexing passive optical network optical line terminal with share protect function according to claim 1 and 2 is characterized in that: the light Transmit-Receive Unit number of described standby optical transceiver module is not more than the number of the light Transmit-Receive Unit that the key light transceiver module needs protection.

4. the Wavelength division multiplexing passive optical network optical line terminal with share protect function according to claim 1 and 2 is characterized in that: use optical switch and multiplexer multiple signals to be combined into one the tunnel in the light Transmit-Receive Unit number of described standby optical transceiver module during more than one.

5. the Wavelength division multiplexing passive optical network optical line terminal with share protect function according to claim 1 and 2 is characterized in that: use mixer multiple signals to be combined into one the tunnel in the light Transmit-Receive Unit number of described standby optical transceiver module during more than one.

6. the Wavelength division multiplexing passive optical network optical line terminal with share protect function according to claim 5 is characterized in that: to adopting the light Transmit-Receive Unit of Wavelength tunable light source in the described standby optical transceiver module, use the wavelength-tunable photodetector.

7. the Wavelength division multiplexing passive optical network optical line terminal with share protect function according to claim 1 and 2; it is characterized in that: when the light Transmit-Receive Unit number of described standby optical transceiver module was one, this light Transmit-Receive Unit used the wavelength-tunable photodetector.

8. according to claim 6 or 7 described Wavelength division multiplexing passive optical network optical line terminals with share protect function, it is characterized in that: described wavelength-tunable photodetector is connected with the broadband light detector by wavelength tunable filter and is constituted.

9. the Wavelength division multiplexing passive optical network optical line terminal with share protect function according to claim 1 and 2 is characterized in that: the signal that the light Transmit-Receive Unit of described standby optical transceiver module sends and receives is by coupler or optical circulator combination.

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