System and method for automatically detecting fiber optic connectivity

Abstract

A system and method for determining optical fiber connectivity between one or more optical transponders (102, 104, ... 106) and an optical multiplexer including a plurality of ports (112, 114, ... 116). During operation, a network controller (110) selects an optical transponder from the one or more optical transponders (102, 104, ... 106); and generates a control signal for the selected optical transponder to adjust the amplitude of an optical signal sent by the selected optical transponder to a port on the optical multiplexer. The network controller (110) determines a measurement result corresponding to the optical signal received at the plurality of ports (112, 114, ... 116); and based on the measurement result, identifies a port on the optical multiplexer as coupled to the selected optical transponder.

Description

Technical Field

[0001] The present disclosure relates generally to optical transport networks (OTNs). More specifically, the present disclosure relates to a system and method capable of detecting optical fiber connectivity between a port of a wavelength selective switch (WSS) and an optical transponder. Background Art

[0002] The rapidly growing demand for network traffic has driven the speed of optical networks (including single-wavelength bit rate and symbol rate) to continue to increase. The most advanced dense wavelength division multiplexing (DWDM) optical network can support up to 192 wavelengths on a pair of optical fibers, with each wavelength transmitting up to 100Gbit / s. Traditional wavelength multiplexing / demultiplexing equipment based on 100GHz-spaced arrayed waveguide gratings (AWG) can no longer meet the requirements of such high-speed optical networks. In addition, due to the rigid channel spacing of AWG, even systems that implement higher-resolution AWGs (e.g., 50GHz-spaced AWGs) face challenges in effectively utilizing the fiber spectrum.

[0003] Flex-grid technology allows flexible spacing between optical channels and can therefore significantly increase the channel capacity of optical fibers. To support high bit rate wavelength add / drop, optical transport networks can replace fixed-interval AWGs with flex-grid wavelength selective switches (WSS). Optical connections to AWGs are typically colored, meaning that a specific wavelength must be connected to a port on the AWG. In contrast, WSS can support colorless connections, meaning that the wavelength can be set under software control and is not fixed by the physical port on the switch. This can simplify the construction of the network, allowing arbitrary connections between optical transport equipment (e.g., transponders) and WSSs. The input / output of a transmission terminal device can be connected to any port on the WSS, regardless of wavelength. However, the optical network management system needs to know the connectivity between the transmission terminal and the WSS (e.g., which terminal device is connected to which port of the WSS) in order to correctly configure the WSS. Summary of the invention

[0004] One embodiment described herein provides a system and method for determining optical fiber connectivity between one or more optical transponders and an optical multiplexer including a plurality of ports. During operation, a network controller selects an optical transponder from the one or more optical transponders; and generates a control signal for the selected optical transponder to adjust the amplitude of an optical signal sent by the selected optical transponder to a port on the optical multiplexer. The network controller determines a measurement result corresponding to the optical signal received at the plurality of ports; and based on the measurement result, identifies a port on the optical multiplexer as coupled to the selected optical transponder.

[0005] In a variation of this embodiment, the optical multiplexer may include a fixed grid wavelength selective switch or a flexible grid wavelength selective switch.

[0006] In a variation of this embodiment, adjusting the intensity of the optical signal includes modulating the amplitude of the optical signal using a unique time domain pattern.

[0007] In a further variation, the time domain pattern comprises one or more pulses, wherein each pulse has a predetermined modulation depth and a predetermined duration.

[0008] In a further variant, the optical signal carries data and has a modulation depth of less than 10%.

[0009] In a further variation, the time domain pattern includes two pulses, each pulse having a predetermined modulation depth selected from two different modulation depths and a predetermined duration selected from a plurality of different durations.

[0010] In a further variation, the control signal includes a unique pattern identifier corresponding to the unique time domain pattern, thereby facilitating the selected transponder to obtain the unique time domain pattern based on the unique pattern identifier.

[0011] In further variations, modulating the amplitude of the optical signal may include using a variable optical attenuator (VOA) or amplifier.

[0012] In a variation of this embodiment, the measurements are obtained by photodiodes associated with various ports on the optical multiplexer.

[0013] In a variation of this embodiment, determining the measurement result may include turning on a performance monitoring function at each port on the optical multiplexer and receiving a performance monitoring result from each port.

[0014] In another variation, adjusting the amplitude of the optical signal includes adjusting a maximum power and a minimum power of the optical signal within the performance monitoring window so that a difference between the maximum power and the minimum power of the optical signal within the performance monitoring window is equal to a predetermined value.

[0015] In a variation of this embodiment, adjusting the intensity of the optical signal includes switching a laser associated with the transponder on and off at predetermined moments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A diagram illustrating an exemplary scenario for automatic detection of fiber connectivity in an optical transport network (OTN) according to one embodiment.

[0017] Figure 2 A plurality of low frequency time domain patterns are shown according to one embodiment.

[0018] Figure 3 A schematic diagram of an exemplary transponder is shown according to one embodiment.

[0019] Figure 4 A schematic diagram of an exemplary wavelength selective switch (WSS) is shown according to one embodiment.

[0020] Figure 5 A time-space diagram is shown of an exemplary process for automatically detecting fiber connectivity between an optical transponder and a port on a wavelength selective switch, according to one embodiment.

[0021] Figure 6 An exemplary scenario for automatic detection of fiber connectivity according to one embodiment is shown.

[0022] Figure 7 An exemplary scenario for automatic detection of fiber connectivity according to one embodiment is shown.

[0023] Figure 8 An exemplary network management and control apparatus according to one embodiment is shown.

[0024] Fig. 9 An exemplary computer system is shown that facilitates a network controller system for automatically detecting fiber connectivity according to one embodiment.

[0025] In the drawings, like reference numerals refer to like graphical elements. DETAILED DESCRIPTION

[0026] The following description is provided to enable any person skilled in the art to make and use the embodiments, and is provided in the context of a specific application and its requirements. Various modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Therefore, the present invention is not limited to the embodiments shown, but should be consistent with the widest scope consistent with the principles and features disclosed herein.

[0027] Overview

[0028] In the present disclosure, a method and system for automatically detecting connectivity between a colorless optical multiplexer and a plurality of optical transmission terminals are provided. In the initial establishment phase of an OTN, a plurality of optical transmission terminals may be connected to an optical multiplexer (e.g., a WSS) via optical fibers to implement wavelength division multiplexing and wavelength division multiplexing (e.g., add / drop) functions. Since the optical multiplexer is colorless, a transmission terminal may be arbitrarily connected to any port on the optical multiplexer. After the optical fiber connection is established, a network management and control module may configure a corresponding port on the optical multiplexer based on the identity of the transmission terminal. In some embodiments, the network management and control module may automatically detect the optical fiber connection between the optical transmission terminal and the port on the multiplexer. More specifically, when configuring a particular transmission terminal (e.g., by specifying an operating wavelength and a bit / symbol rate), the network management and control module may also assign a unique mode identifier corresponding to a particular time domain mode to the transmission terminal, thereby facilitating the transmission terminal to encode the optical signal it transmits using this time domain mode. In some embodiments, this encoding does not interrupt service, which means that the transmission terminal can communicate with other network elements regularly. In some embodiments, the service may be briefly interrupted to allow the transmission terminal to transmit the time domain pattern to the connection port on the optical multiplexer. When the coded optical signal is received at a particular port, the optical multiplexer may extract the time domain pattern and determine the identity of the transmission terminal based on a unique pattern identifier corresponding to the time domain pattern. The network management and control module may then configure the particular port on the optical multiplexer based on the identity of the transmission terminal.

[0029] Automatic detection of fiber connectivity

[0030] Compared to AWG with fixed channel spacing, flex-grid WSS can provide higher spectral efficiency and flexibility in interfacing with transmission terminals from different equipment vendors. In addition, the colorless nature of WSS makes the establishment phase of OTN simpler because there are no longer wavelength restrictions when connecting transmission terminals (e.g., transponders) and WSS. However, this also poses a challenge to the network management system, which needs to know the fiber connection information to configure the WSS. The traditional approach relies on manually entering the fiber connection information during the establishment phase. However, if the OTN has a large number of network elements, this manual solution may be difficult to implement. In addition, in the case where the network management system takes over the control of a previously established OTN, the fiber connection information may not be available for manual entry. It is desirable that the network management system has the ability to automatically detect fiber connectivity.

[0031] BRIEF DESCRIPTION OF THE DRAWINGS Figure 1A diagram showing an exemplary scenario for automatic detection of fiber connectivity in an optical transport network (OTN) according to one embodiment. The OTN 100 may include a plurality of transport terminals, such as transponders 102, 104, and 106, and a WSS 108. The OTN 100 may also include a network controller 110, which may communicate with the transport terminals and the WSS 108 via a network 120.

[0032] The optical transponders 102-106 may include devices from different vendors and may provide different data rates and / or wavelengths. The WSS 108 may be a flexible grid wavelength selective switch or a fixed grid wavelength selective switch. The WSS 108 may include multiple wavelength ports, and each transponder may be connected to a port on the WSS 108 via an optical fiber pair, where one optical fiber is used for transmission and one optical fiber is used for reception. For simplicity, the fiber pair may also be referred to as simply a fiber. For example, transponders 102, 104, and 106 may be connected to ports 112, 114, and 116 on the WSS 108 via optical fibers 122, 124, and 126, respectively. The connection between the transponder and the port on the WSS 108 may be arbitrary, meaning that the optical fiber connected to the transponder may be connected to any port on the WSS 108. The operator who sets up these connections may choose to connect them randomly or follow a certain principle (e.g., a proximity principle to minimize the length of the connecting optical fiber).

[0033] Once the fiber connection is established, the network management system resident on the network controller 110 can take over the control of the optical elements in the OTN 100. The network controller 110 can establish optical channels (OCHs) for the OTN 100, where each optical channel (OCH) represents an end-to-end optical path between a pair of transponders. Establishing an optical channel may involve sending control commands to the transponders. For example, the network controller 110 can configure the wavelength and data rate of a specific transponder (e.g., transponder 102), and turn on the specific transponder after it is properly configured.

[0034] The optical signal from a particular transponder may be received at a particular port on WSS 108 via an optical fiber connecting the transponder and the WSS port. In order for WSS 108 to perform appropriate wavelength switching based on the wavelength of the received signal, network controller 110 needs to know which transponder is connected to which port on WSS 108 in order to configure the corresponding port on WSS 108. For example, controller 110 may need to configure the wavelength of a tunable laser for a particular port.

[0035] In some embodiments, in order to facilitate the network controller 110 to automatically detect the connectivity of the optical fibers 122-126 (i.e., to detect which transponder is connected to which WSS port), when configuring the transponder, the WSS 108 may send a unique mode identifier to the transponder. The mode identifier may correspond to a low-frequency time domain mode. The WSS 108 may maintain a mapping between the mode identifier and the transponder's identifier. After being turned on and starting to send optical signals to the connection port on the WSS 108, the transponder may send an optical signal modulated using the low-frequency time domain mode to the connection port on the WSS 108. A variety of modulation schemes may be used, including amplitude modulation or power modulation schemes. In some embodiments, the low-frequency time domain mode may be used to modulate the amplitude of a normal optical signal (e.g., an optical signal carrying data traffic between the transponder and the WSS 108). More specifically, the amplitude modulation may be weak so that it does not interfere with the conventional service signal sent by the transponder.

[0036] Upon receiving the optical signal from the transponder, the WSS 108 may extract the low-frequency time domain pattern. For example, if the low-frequency time domain pattern is used for amplitude modulation, the WSS 108 may detect the low-frequency envelope of the optical signal. Based on the extracted low-frequency time domain pattern, the WSS 108 may determine a pattern identifier and send the determined pattern identifier to the network controller 110 together with the identification of the port receiving the optical signal. The network controller 110 may then identify the transponder that sent the optical signal based on the recorded mapping between the pattern identifier and the transponder's device ID, thereby enabling automatic detection of optical fiber connectivity.

[0037] In some embodiments, each time domain pattern may include a periodic signal whose amplitude varies over time. The time domain pattern may be used to modulate the amplitude of the optical signal output by the optical transponder, and the amplitude of the time domain pattern may represent the modulation depth. For example, a higher amplitude may represent a shallower modulation depth, while a lower amplitude may represent a deeper modulation depth. By assigning a unique time domain pattern to each transponder to allow the transponder to modulate its emitted optical signal using a unique time domain pattern, the system provides a way for the network controller to determine the identity of the transponder that sends the signal to a specific port on the WSS. The simplest form of a time domain pattern may be a square wave, with each transponder assigned a unique frequency. However, using frequency alone to distinguish transponders may be challenging because at lower resolutions it can only be applied to a limited number of transponders, while at higher resolutions, a high-speed detector would be required for each WSS port. Similarly, using amplitude alone would present similar challenges. In order to allow simple detection of a large number of time domain patterns, it is desirable to design time domain patterns with varying amplitudes and frequencies.

[0038] Figure 2A plurality of low frequency time domain patterns are shown according to one embodiment. Figure 2 In the example shown, each time domain pattern can be a periodic signal with a unique waveform. Each period of the time domain pattern can include a plurality of low amplitude square pulses of different widths (e.g., pulses 206 and 208) separated from each other by high amplitude square pulses of fixed width (e.g., pulses 202 and 204). In fact, the high amplitude square pulses of fixed width can be regarded as protection time, and the various widths and depths of the low amplitude square pulses can be used to distinguish transponders. More specifically, what distinguishes transponders is the unique combination of the width and depth of the low amplitude pulses (e.g., pulses 202 and 204) in each time domain pattern.

[0039] exist Figure 2 In the example shown, each cycle of the time domain pattern may include two low-amplitude square pulses, and there are two variables in terms of modulation depth: d1 and d2. In some embodiments, the modulation depths d1 and d2 may be 5% and 10%, respectively, meaning that the amplitudes of the transmitted optical signals are modulated to 95% and 90% of their original values. Other combinations (e.g., 4% and 8%, or 3% and 7%) are also possible. However, in order to ensure that the transmission of low-frequency time domain patterns does not interfere with normal signal transmission, it is desirable to limit the modulation depth to no more than 10%. Larger modulation depths may have a negative impact on the optical signal-to-noise ratio (OSNR) of the transmitted optical signal. On the other hand, the width variation can have a larger range. In Figure 2 In the embodiment, the protection time is represented as "T", and the width of each low-amplitude pulse can be a multiple of the protection time, represented as "mT" and "nT", respectively, where m and n are both positive integers.

[0040] Figure 2 The upper diagram of shows a time domain pattern with a first low amplitude pulse having a modulation depth d1 and a width m1T and a second low amplitude pulse having a modulation depth d2 and a width n1T. Figure 2 The middle diagram of shows a time domain pattern, whose first low amplitude pulse has a depth d1 and a width m2T, and whose second low amplitude pulse has a depth d2 and a width n2T. Figure 2 The bottom diagram shows the time domain pattern, where the first low amplitude pulse has a depth d1 and a width m k T, whose second low amplitude pulse has depth d1 and width n kT. In practice, each unique time-domain pattern can be identified using a set of numbers that describe a pair of pulses: [(m,d),(n,d)] where m and n are the widths of the pulses and d is the depth of each pulse. The sequence of pulses is irrelevant because the patterns can be considered the same if the two pulses switch order, meaning that [(m,d),(n,d)] and [(n,d),(m,d)] refer to the same pattern. Figure 2 In the example shown, the pulses [(m1, d1), (n1, d2)] can be used to identify mode_1, the pulses [(m2, d1), (n2, d2)] can be used to identify mode_2, and the pulses [(m k ,d1),(n k ,d1)]Identify pattern_k.

[0041] from Figure 2 As can be seen in , the period of each time domain pattern can be expressed as (m+n+2)T. It is hoped that such a time period is a reasonable value. A pattern that is too long will reduce the efficiency of detecting fiber connectivity, and a pattern that is too short will require a high-speed detector at the WSS port. Considering that a low-speed optical detector at a WSS port may have a response time of about 100 ms, it is reasonable to have a protection time (which reflects the time domain granularity of the pattern) of about several hundred milliseconds (ms) or more. In some embodiments, the protection time T can be about 0.5 seconds, and the integers m and n can be between 1 and 6 to ensure a reasonable pattern period. Therefore, the longest pattern period can be about 7 seconds. Other pattern ranges are also possible.

[0042] exist Figure 2 In the example, each time domain pattern has a unique combination of pulses of a specific depth and width. The number of patterns (denoted as N) that can be provided using this scheme is determined based on the number of pulses (denoted as P), the number of depth variations (denoted as D), and the number of width variations (denoted as W), where N = (DW) P / P! Given that there are two low-amplitude pulses per cycle (i.e., P=2), two depth variations (D=2), and up to six width variations (W=6), there can be up to 72 unique patterns. A typical WSS may have 64 ports; therefore, 72 unique patterns are sufficient to distinguish 64 transponders coupled to these 64 ports.

[0043] Apart from Figure 2 In addition to the scheme shown, other types of time domain patterns can also be used. For example, additional numbers of depth or width variations can be used, or additional pulses can be included in each pattern cycle. Moreover, in addition to square pulses, the time domain pattern can also have other shapes, such as sine or triangle.

[0044] Figure 3A schematic diagram of an exemplary transponder according to one embodiment is shown. The transponder 300 may include a control unit 302 , a continuous wave (CW) laser 304 , a modulator 306 , and a modulator driver 308 .

[0045] The control unit 302 can communicate with a remote network management and control module (e.g., Figure 1 In some embodiments, the control unit 302 may communicate with the network controller 110 as shown. More specifically, the control unit 302 may receive commands from the network controller 110 and send status reports to the network controller 110. In some embodiments, the control unit 302 may receive an emission wavelength and a mode identifier assigned to the transponder 300 from the network management and control module. The control unit 302 may configure the CW laser 304 according to the emission wavelength. In addition, the control unit 302 may obtain a time domain mode based on the mode identifier received from the network management and control module. In some embodiments, the time domain mode and the mapping relationship between the time domain mode and the mode identifier may be stored in the hardware (e.g., a line card) of the transponder 300.

[0046] The CW laser 304 may be a tunable laser or may include multiple single wavelength lasers. The CW laser 304 may be configured by the control unit 302 to emit CW light of a specified wavelength. The modulator 306 may be configured to modulate the CW light emitted by the CW laser 304. The modulator driver 308 may configure the modulator 306. For example, the modulator driver 308 may configure the modulator 306 so that in addition to the high bit rate modulation required to encode the information in the transmitted optical signal, a low frequency modulation may be applied to encode the identity information associated with the transponder 300. More specifically, the modulator driver 308 may configure the modulator 306 to apply additional modulation using a low frequency time domain pattern, so that the amplitude of the light varies slightly. Because the additional modulation slightly changes the amplitude of the modulated light, the modulated light may be considered to "flicker", and the modulated portion of the optical signal may be referred to as a flicker. For example, Figure 2 The optical signal modulated by pulses 202 and 204 shown in FIG. 1 may be referred to as a flash. The unique combination of the length and amplitude of the flash carries the transponder identity information to the WSS, allowing the WSS to extract such information from the modulated signal.

[0047] In some embodiments, rather than using a modulator, flicker is generated by adjusting the attenuation or amplification of the optical signal. More specifically, the control unit 302 may control a variable optical attenuator (VOA) to Figure 3 304 according to the time domain mode. Optionally, the control unit 302 may control an amplifier (e.g., an erbium-doped fiber amplifier (EDFA)) which Figure 3The scope of the invention is not limited by the modulation scheme, as long as the amplitude of the optical signal can be modulated to produce flashes, and unique combinations of flash amplitude and duration can be used to distinguish transponders emitting these flashes.

[0048] Figure 4 4 shows a schematic diagram of an exemplary wavelength selective switch (WSS) according to one embodiment. WSS 400 may include an optical decoupler 402, a low-speed photodetector (PD) 404, a control unit 406, and a WSS module 408. For simplicity, Figure 4 A WSS 400 with a single port is shown. The structure of a WSS with multiple ports is similar.

[0049] Each port of the WSS 400 may include an optical decoupler 402 and a low-speed PD 404. A small portion of the optical signal arriving at a specific port on the WSS 400 may be tapped by the optical decoupler 402 and sent to the low-speed PD 404. The low-speed PD 404 converts the optical signal into an electrical signal. Due to the long response time of the PD 404 (e.g., 100ms), the converted electrical signal actually captures the envelope of the optical signal, and the envelope is a low-frequency time pattern. Please note that most commercially available WSSs have a built-in PD for power monitoring at each port. This built-in PD is typically a low-cost and low-speed PD. In the case where each input port of the WSS does not include a PD, a low-cost PD may be added externally to couple to each WSS port.

[0050] The control unit 406 can communicate with a remote network management and control module (e.g., Figure 1 The control unit 406 may communicate with the network controller 110 shown in FIG. 400 . For example, the control unit 406 may receive configuration information from the network management and control module, and may use such configuration information to configure the switching behavior of the WSS module 408. In addition, the control unit 406 may maintain a mapping relationship between the waveform of the time domain module and the model identifier. Once the PD 404 sends its output (e.g., a specific time domain pattern) to the control unit 406, the control unit 406 may determine a pattern identifier corresponding to the time domain pattern extracted by the PD 404 based on the mapping relationship. The control unit 406 may then send the determined pattern identifier to the remote network management and control module, which may then identify the transponder corresponding to the determined pattern identifier. The identified transponder is a transponder connected to a specific port on the WSS 400. Based on the wavelength of the identified transponder, the remote network management and control module may send configuration information to the control unit 406 to facilitate the control unit 406 to configure the WSS module 408.

[0051] Figure 5A time-space diagram of an exemplary process for automatically detecting optical fiber connectivity between an optical transponder and a port on a wavelength selective switch according to one embodiment is shown. During operation, the network management and control module 502 sends configuration information to the optical transponder 504 (operation 506). This can be done during the establishment phase of the optical channel. The configuration information can include a transmission wavelength and a mode identifier.

[0052] Upon receiving the configuration information, the responder 504 obtains the low frequency time domain pattern corresponding to the received pattern identifier (operation 508). The responder 504 may store multiple unique time domain patterns in its hardware (e.g., line card). In some embodiments, the time domain pattern may be similar to Figure 2 The mode shown, such as Figure 2 As shown, each pattern includes a plurality of low-amplitude pulses of different widths and amplitudes. The network management and control module 502 and the transponder 504 both store the mapping relationship between the pattern identifier and the pattern. Figure 2 The pattern format is similar to that shown, and the pattern identifier can specify the duration and depth of each low amplitude pulse.

[0053] The optical transponder 504 turns on its laser according to the specified wavelength (operation 510) and modulates the optical signal using the identified low-frequency time domain pattern (operation 512). Note that this modulation is in addition to the modulation of the CW light based on the data to be transmitted. Because the low-frequency time domain pattern has a small modulation depth (e.g., less than 10%), this additional modulation affects the data modulated light at a minimal level. The optical transponder 504 sends the modulated optical signal to a specific port on the WSS 514 through the optical fiber (operation 516).

[0054] Upon receiving the modulated optical signal, a low-speed PD coupled to a port of the WSS 514 extracts a low-frequency time domain pattern from the modulated optical signal (operation 518). The PD may typically have a response time of 100 ms and is therefore capable of detecting a time domain pattern having a minimum pulse width of 0.5 seconds or greater. The WSS 514 may then determine a pattern identifier based on the extracted time domain pattern (operation 520). In some embodiments, the WSS 514 may make such a determination based on a mapping relationship between the time domain pattern and the pattern identifier.

[0055] The WSS 514 may then transmit the determined pattern identifier to the network management and control module 502 (operation 522). The network management and control module 502 may then identify the transponder 504 as a transponder connected to a specific port on the WSS 514 based on the pattern identifier (operation 524). For example, the network management and control module 502 may maintain a record of which pattern was sent to which transponder. When the network management and control module 502 receives a specific pattern identifier, it may search its record to determine which transponder received the specific pattern identifier. In response to determining that the transponder 504 is connected to a specific port on the WSS, the network management and control module may configure the specific port on the WSS based on the wavelength and possible signal amplitude of the transponder 504 (operation 526).

[0056] In addition to modulating the amplitude of the optical signal transmitted by the transponder using a unique low-frequency time-domain pattern, in some embodiments, each transmitter can modulate the power of the transmitted optical signal within a predetermined time window (e.g., by increasing or decreasing the power output of a CW laser). The amount of power modulation can be unique for each transponder. By observing the power difference of the optical signal transmitted within the time window, the connectivity of the optical fiber can be determined.

[0057] In some embodiments, the network management and control module may use the existing built-in performance monitoring functionality of the WSS to automatically detect fiber connectivity. Figure 6 An exemplary scenario for automatic detection of fiber connectivity according to one embodiment is shown. In this example, the network management and control module uses built-in performance monitoring functions to implement automatic detection of fiber connectivity. At time t0, the network management and control module can start a performance monitor (PM) bin by clearing the current PM bin for all ports on the WSS. At time t1, the network management and control module can send a command to the transponder to adjust the output power of each transponder; and at time t2, the network management and control module can send a command to the transponder to adjust the output power of each transponder to its original value. At time t3, the PM bin is closed, allowing the network management and control module to calculate PM results for each WSS port. The duration of each PM bin can last from hundreds of milliseconds to several minutes. In some embodiments, the PM result can include a power variation parameter that measures the difference between the maximum power and the minimum power received at the WSS port. Therefore, if the output power of the transponder can be adjusted in such a way that the difference between the maximum and minimum output powers within the PM bin can be a unique value for each transponder, the network management and control module can use the PM results to distinguish between transponders.

[0058] exist Figure 6In the illustrated embodiment, the output power of transponder_1 first increases to a value above its normal output power, then decreases to a value below its normal output power, and then returns to its normal transmit power. For transponder_1, the difference between its maximum and minimum output powers in the PM bin is delta_1. Similarly, the output power of transponder_2 increases, then decreases, and then returns to its normal value. For transponder_2, the difference between its maximum and minimum output powers in the PM bin is delta_2. On the other hand, for transponder_3, its output power only decreases to a certain value before returning to its normal value. For transponder_3, the difference between its maximum and minimum output powers in the PM bin is delta_3. Because each of delta_1, delta_2, and delta_3 has a unique value (for example, delta_1 can be 1dBm, delta_2 can be 2dBm, and delta_3 can be 0.5dBm), the network management and control module can use this information to determine the connectivity between the transponder and the WSS port.

[0059] Using built-in PM to detect fiber connectivity does not require any changes to the hardware and software or firmware of the transponder and WSS. For example, it is no longer necessary to add an external PD capable of detecting sub-second fluctuations in the amplitude of the optical signal to each WSS port. Instead, a simple PD for collecting PM data is sufficient. However, the power adjustment range may be limited. In order to avoid interruption to the conventional service signal, it is preferred to limit the power change to a few (e.g., less than 3) dB, so if the number of transponders is relatively large, it is difficult to achieve. Another method is to use multiple PM bins to detect power changes. For example, a large number of transponders can be grouped into multiple groups, each of which has a small number of transponders. The network management and control module can adjust the power of a group of transponders in a specific PM bin. After determining the connectivity of this group of transponders, the network management and control module can start the next PM bin and adjust the output power of the next group of transponders. In this way, the fiber connectivity of a larger number of transponders can be determined without increasing the power adjustment range. However, this method will extend the time required to detect the connectivity of all transponders and may be more susceptible to fluctuations in fiber insertion loss.

[0060] In an alternative embodiment, in order to detect the connectivity of a specific transponder, the network management and control module can also initialize a specific detection window and shut down the conventional optical signal transmission of the transponder during the specific detection window. Instead of an optical signal carrying data, the network management and control module can turn on the CW laser of the transponder to send a CW signal within the detection window for a predetermined duration. By determining which WSS port receives the CW signal in a specific detection window, the network management and control module can automatically detect the fiber connectivity of the transponder. In some embodiments, the network management and control module can detect the fiber connectivity of a single transponder within the detection window. Optionally, the network management and control module can detect the fiber connectivity of multiple transponders within a single detection window. To this end, the CW laser of each transponder can be turned on and off according to a specific pattern.

[0061] Figure 7 An exemplary scenario for automatic detection of fiber connectivity according to one embodiment is shown. Figure 7 In the scenario shown, transponders_1-4 are connected to different ports on the WSS via optical fibers. The network management and control module may be configured to determine the optical fiber connectivity of transponders_1 and transponders_2 within a detection window starting from t0.

[0062] More specifically, at t0, the network management and control window may instruct the WSS to start monitoring the input power at each port. After a predetermined delay (e.g., 0.5s), at time t1, the network management and control module receives an acknowledgement from the WSS, and then at time t2, turns off the output power of transponder_1 and transponder_2, while allowing transponder_3 and transponder_4 to operate normally. More specifically, the CW lasers of transponder_1 and transponder_2 may be turned off. Figure 7 The dashed line in represents the power of the optical signal carrying data.

[0063] At a specific moment within the detection window (for example, at time t3), the network management and control module can turn on the CW lasers of transponder_1 and transponder_2. At time t4, the CW laser of transponder_1 can be turned off. At time t5, the CW laser of transponder_2 can be turned on again; and at time t6, the CW laser of transponder_2 is turned off again. At time t7, the network management and control module can instruct the WSS to stop monitoring the input power of each port and report the power monitoring results to the network management and control module. The WSS ports connected to transponder_1 and transponder_2 will observe Figure 7The unique power switching pattern shown. On the other hand, the CW lasers of transponder_3 and transponder_4 always remain on, and the power observed at the corresponding WSS port will depend on the presence or absence of the optical signal carrying data. Therefore, by turning the laser of each transponder on and off according to a specific pattern, the network management and control module can automatically detect the fiber connectivity. To ensure that the low-speed PD can detect the power changes at each WSS port, the duration that the laser remains on should be at least several hundred ms. Figure 7 Faced with Figure 6 The same challenges shown above, more specifically, are that it is difficult to detect a large number of transponders within a relatively small detection window (e.g., a window lasting a few seconds). A longer detection window can allow connectivity detection for a large number of transponders. However, this will also extend the time required to detect the connection between the transponder and the WSS port. In addition, turning off the laser in the transponder will interrupt normal data traffic.

[0064] In extreme cases, the network management and control module can turn off the lasers of all transponders and then turn them on one at a time. By observing the power reception sequence of the WSS port, the network management and control module can determine the fiber connectivity of the transponder. Although simple, this method interrupts normal signal transmission and can therefore only be used during the initial establishment phase of a new network. In addition, for a large number of transponders, this method also requires a relatively long detection time window.

[0065] Figure 8 An exemplary network management and control device according to one embodiment is shown. The network management and control device 800 may include a transponder communication module 802 , a mapping table 804 , a multiplexer communication module 806 , a fiber connectivity determination module 808 , a multiplexer configuration module 810 , and a network management module 812 .

[0066] The transponder communication module 802 can communicate with the transponder. In some embodiments, the transponder communication module 802 can send configuration information (e.g., wavelength assignment) to the transponder. In addition, the transponder communication module 802 can also send various control information that controls the operation of the transponder to facilitate automatic detection of connectivity between the transponder and the WSS. In some embodiments, the control information may include an identifier that identifies a unique time domain pattern that can be used to modulate an optical signal sent by the transponder. In some embodiments, the control information may include a power adjustment parameter for adjusting the transmit power of the transponder. In other embodiments, the control information may include a command that can turn on and off a CW laser of the transponder.

[0067] In some embodiments, mapping table 804 can store the mapping relationship between the time domain mode identifier and the transponder. Each time a transponder is added to the network (e.g., connected to WSS), an entry is added to mapping table 804 to map the identity of the transponder to the identifier of the time domain mode. Alternatively, mapping table 804 can store other mapping information, such as the mapping between power adjustment parameters and the transponder or the mapping between the laser switch sequence and the transponder. Depending on the type of control information sent to the transponder by the transponder-communication module 802, mapping table 804 can store different types of mapping information.

[0068] The multiplexer communication module 806 can communicate with a wavelength selective switch (WSS). In some embodiments, the multiplexer communication module 806 can receive a time domain mode identifier from a specific port of the WSS. The mode identifier can be used to determine the transponder connected to the specific port. In an alternative embodiment, the multiplexer communication module 806 can send a performance monitoring (PM) command and receive a PM result from the WSS port. Once the connectivity between the transponder and the WSS port is determined, the multiplexer communication module 806 can send multiplexer configuration information to the WSS.

[0069] The fiber connectivity determination module 808 determines the connectivity between the transponder and the WSS port based on the controlled amplitude of the optical signal received at each WSS port. For example, the fiber connectivity determination module 808 can match the time domain pattern used to modulate the optical signal at a specific transponder with the time domain pattern detected by the low-speed PD at the corresponding WSS port, thereby determining that the specific transponder is connected to the corresponding WSS port via optical fiber. Similarly, when using the PM function, the fiber connectivity determination module 808 can also match the power adjustment range at the specific transponder with the PM result measured at the corresponding WSS port, thereby determining that the specific transponder is connected to the corresponding WSS port via optical fiber.

[0070] The multiplexer configuration module 810 can configure the WSS based on the determined fiber connectivity between the transponder and the WSS. More specifically, once the fiber connectivity determination module 808 determines that a particular WSS port is connected to a transponder of a particular wavelength, the multiplexer configuration module 810 can configure the particular WSS port according to the connected transponder (e.g., configure the center frequency of a tunable laser for the WSS port).

[0071] The network management module 812 may perform various network management functions, such as allocating wavelengths and / or modulation formats at each transponder, performance monitoring, fault detection, etc.

[0072] Fig. 9An exemplary computer system is shown that facilitates a network controller system for automatically detecting fiber connectivity according to one embodiment. Computer system 900 includes a processor 902, a memory 904, and a storage device 906. Computer system 900 can be coupled to a display device 910, a keyboard 912, a pointing device 914, and can also be coupled to a network 908 via one or more network interfaces. Storage device 906 can store an operating system 918, a network controller system 920, and data 940.

[0073] The network-controller system 920 may include instructions that, when executed by the computer system 900, may cause the computer system 900 to perform the methods and / or processes described in the present disclosure. The network-controller system 920 may include instructions for communicating with a transponder (transponder communication module 922), instructions for communicating with an optical multiplexer (multiplexer communication module 924), instructions for determining fiber connectivity between a transponder and a multiplexer port (fiber connectivity determination module 926), instructions for configuring a multiplexer (multiplexer configuration module 928), and instructions for managing a network (network management module 930). The data 940 may include a mapping table 942.

[0074] In general, embodiments of the present invention provide a solution for automatically detecting fiber connectivity between transponders and multiplexer ports. A network controller may send control information to a transponder to modulate the amplitude of an optical signal sent by the transponder. In some embodiments, the amplitude of a high-speed data-carrying optical signal may be modulated using a unique time domain pattern assigned to the transponder by the network controller. The time domain pattern may include one or more pulses of variable depth and width. The unique combination of the depth and width of the pulse determines the uniqueness of the time domain pattern. The modulation depth of the time domain pattern may be kept small to minimize the impact of the high-speed data-carrying optical signal on OSNR. A low-speed PD (e.g., a PD with a response time of 100ms) equipped by a WSS port may extract a time domain pattern from a received optical signal, and the WSS port then sends the extracted time domain pattern to the network controller. The network controller matches the time domain pattern received from a specific WSS port with the time domain pattern assigned to a specific transponder to determine that the specific WSS port is connected to the specific transponder. Alternatively, the network controller may use the existing PM function of the WSS to detect fiber connectivity. By manipulating the transponder output power fluctuations within the PM bin, and by comparing the PM results with the manipulated power fluctuations of the transponder output power, the network controller can match the WSS port to the transponder. In another embodiment, data communications can be interrupted, and the transponder's laser can be turned off and on at predetermined, non-overlapping moments to allow the network controller to match the WSS port receiving optical power to the transponder whose laser is turned on.

[0075] The methods and processes described in the detailed description section may be embodied as code and / or data, which may be stored in a computer-readable storage medium as described above. When a computer system reads and executes the code and / or data stored on the computer-readable storage medium, the computer system executes the methods and processes embodied as data structures and code and stored in the computer-readable storage medium.

[0076] In addition, the above methods and processes can be implemented in digital electronic circuits; or in computer software, firmware or hardware. Hardware modules or devices may include, but are not limited to, application specific integrated circuit (ASIC) chips, field programmable gate arrays (FPGAs), dedicated or shared processors that execute a specific software module or piece of code at a specific time. And other programmable logic devices now known or later developed. When the hardware modules or devices are activated, they execute the methods and processes included therein.

[0077] The above techniques may be implemented using one or more computer program products. Programmable processors and computers may be included in or packaged as mobile devices. Processing and logic flows may be performed by one or more programmable processors or by one or more programmable logic circuits. General and special computing devices and storage devices may be interconnected via a communication network.

[0078] The above description of various embodiments is for illustration and description purposes only. They are not intended to be exhaustive or to limit the present invention to the disclosed forms. Therefore, many modifications and variations will be apparent to those skilled in the art. In addition, the above disclosure is not intended to limit the present invention.

Claims

1. A method for determining optical fiber connectivity between one or more optical transponders and an optical multiplexer comprising a plurality of ports, the method comprising: selecting, by the network controller, an optical transponder from the one or more optical transponders; generating a control signal for the selected optical transponder to adjust the amplitude of an optical signal transmitted by the selected optical transponder to a port on the optical multiplexer; determining measurements corresponding to optical signals received at the plurality of ports; as well as A port on the optical multiplexer is identified, by the network controller, as being coupled to the selected optical transponder based on the measurement result.

2. The method according to claim 1, wherein: The optical multiplexer includes a fixed grid wavelength selective switch or a flexible grid wavelength selective switch. The method of claim 1 , wherein adjusting the amplitude of the optical signal comprises modulating the amplitude of the optical signal using a unique time-domain pattern.

4. The method according to claim 3, wherein: The time domain pattern includes one or more pulses, each pulse having a predetermined modulation depth and a predetermined duration.

5. The method according to claim 4, wherein: The optical signal carries data, and wherein the modulation depth is no greater than 10%.

6. The method according to claim 4, wherein: The time domain pattern includes two pulses, each pulse having a predetermined modulation depth selected from two different modulation depths and a predetermined duration selected from a plurality of different durations.

7. The method according to claim 3, characterized in that The control signal includes a unique pattern identifier corresponding to a unique time-domain pattern, thereby facilitating the selected optical transponder to obtain the unique time-domain pattern based on the unique pattern identifier.

8. The method of claim 3, wherein modulating the amplitude of the optical signal comprises using a variable optical attenuator (VOA) or an amplifier.

9. The method according to claim 1, wherein: The measurements are obtained by photodiodes associated with each port on the optical multiplexer.

10. The method of claim 1, wherein determining the measurement result comprises: turning on a performance monitor function at each port of the optical multiplexer; and Receive performance monitoring results from each port.

11. The method according to claim 10, wherein: Adjusting the amplitude of the optical signal includes: adjusting the maximum power and the minimum power of the optical signal within the performance monitor window so that the difference between the maximum power and the minimum power of the optical signal within the performance monitor window is substantially equal to a predetermined value.

12. The method of claim 1, wherein adjusting the amplitude of the optical signal comprises switching a laser associated with the optical transponder on and off at predetermined times.

13. The method of claim 1, wherein the one or more optical transponders include optical transponders manufactured by different vendors.

14. A network controller system for determining optical fiber connectivity between one or more optical transponders and an optical multiplexer comprising a plurality of ports, the network controller system comprising: Processor; and a storage device coupled to the processor and storing instructions, the instructions, when executed by the processor, causing the processor to perform a method, wherein the method comprises: selecting an optical transponder from the one or more optical transponders; generating a control signal for the selected optical transponder to adjust the amplitude of an optical signal transmitted by the selected optical transponder to a port on the optical multiplexer; determining measurements corresponding to optical signals received at the plurality of ports; as well as Based on the measurement results, a port on the optical multiplexer is identified as being coupled to the selected optical transponder.

15. The network controller system of claim 14, wherein the optical multiplexer comprises a fixed grid wavelength selective switch or a flexible grid wavelength selective switch.

16. The network controller system of claim 14, wherein adjusting the amplitude of the optical signal comprises modulating the amplitude of the optical signal using a unique time domain pattern.

17. The network controller system according to claim 16, wherein: The time domain pattern includes one or more pulses, each pulse having a predetermined modulation depth and a predetermined duration.

18. The network controller system of claim 17, wherein the optical signal carries data, and wherein the modulation depth is no greater than 10%.

19. The network controller system according to claim 17, wherein: The time domain pattern includes two pulses, each pulse having a predetermined modulation depth selected from two different modulation depths and a predetermined duration selected from a plurality of different durations.

20. The network controller system according to claim 16, wherein: The control signal includes a unique pattern identifier corresponding to a unique time-domain pattern, thereby facilitating the selected optical transponder to obtain the unique time-domain pattern based on the unique pattern identifier.

21. The network controller system according to claim 16, wherein: Modulating the amplitude of the optical signal includes using a variable optical attenuator (VOA) or an amplifier.

22. The network controller system according to claim 14, wherein: The measurements are obtained by photodiodes associated with each port on the optical multiplexer.

23. The network controller system of claim 14, wherein determining the measurement result comprises: Turning on the performance monitor function at each port of the optical multiplexer; and Receive performance monitoring results from each port.

24. The network controller system according to claim 23, wherein: Adjusting the amplitude of the optical signal includes: adjusting the maximum power and the minimum power of the optical signal within the performance monitor window so that the difference between the maximum power and the minimum power of the optical signal within the performance monitor window is substantially equal to a predetermined value.

25. The network controller system according to claim 14, wherein: Adjusting the amplitude of the optical signal includes switching a laser associated with the optical transponder on and off at predetermined moments.

26. The network controller system of claim 14, wherein the one or more optical transponders include optical transponders manufactured by different vendors.

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