Systems, methods and apparatus for monitoring optical performance

Abstract

The disclosed system and method are designed for monitoring optical performance, comprising: receiving an optical channel signal, wherein the optical channel signal is superimposed with a tuning point (PT) signal; operating a local oscillator (LO) including a tunable laser in a coarse scan mode and a fine scan mode, and generating different LO signals depending on the mode in which the LO is operating; merging the optical channel signal with at least one LO signal generated by the LO to generate a merged optical signal; detecting the merged optical signal and converting the merged optical signal into an electrical signal; amplifying the electrical signal; converting the amplified electrical signal into a digital signal; processing the digital signal and extracting channel-specific information included in the PT signal; calculating channel power based on the channel-specific information; and maintaining a management table.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit and priority of U.S. non-provisional patent application No. 17 / 126,991, filed on December 18, 2020, entitled “System, Method and Apparatus for Monitoring Optical Performance”. Technical Field

[0003] This disclosure generally relates to optical networks, and specifically to systems and methods for monitoring optical performance. Background Technology

[0004] In addressing high data throughput requirements, fiber-based communication systems, such as dense wavelength division multiplexing (DWDM) optical transmission and switching systems, are used to combine multiple optical signals operating at different wavelengths and simultaneously transmit these multiple optical signals at high speed along the optical fiber.

[0005] Optical performance monitoring is commonly used to manage high-capacity DWDM optical transmission and switching systems in Next Generation Networks (NGN). Typically, optical performance monitoring involves assessing the quality of the data channel by measuring its optical characteristics, rather than directly examining the transmitted bit sequence. Optical performance monitoring provides a potential mechanism to improve transmission control and physical layer fault management in DWDM optical transmission and switching systems.

[0006] In optical communications, optical performance monitoring typically serves to: ensure proper switching in reconfigurable optical add-drop multiplexers, set the level of dynamic equalization of optical amplifier gain, and provide system alarms and error warnings for lost or non-compliant optical channels.

[0007] In DWDM networks, the optical component used for this purpose is called an optical performance monitor (OPM). The OPM measures the channel power, wavelength, spectrum, and optical signal-to-noise ratio (OSNR) for each channel. The OPM is an indispensable device for the operation and maintenance (OAM) of DWDM optical transmission and switching systems.

[0008] OPM is essentially a miniature optical spectrum analyzer that measures the spectrum across the entire transmission band (e.g., C-band) with a resolution far exceeding the channel width and obtains the power of each channel.

[0009] Typically, tunable optical filters are used to obtain the spectrum. The passband of an optical filter is usually on the order of several GHz. This spectral resolution may not meet the requirements of modern high-capacity DWDM optical transmission and switching systems, which require sub-GHz resolution to monitor the signal spectrum and the filtering effect of optical filters in the link, as well as laser frequency / wavelength drift.

[0010] Some existing technologies do not employ tunable optical filters but instead rely on coherent OPM to measure the spectrum. This involves using a tunable laser in a local oscillator (LO) and measuring the beat frequency between the LO and the signal under test. The resolution is determined by the laser linewidth and the circuit bandwidth. This allows for the easy achievement of high resolution (e.g., better than 0.1 GHz).

[0011] While coherent OPM offers very good spectral resolution, it requires a large number of measurement samples and a long measurement time (on the order of 1 second) for scanning (scanning across the entire wavelength range, typically C-band, L-band, or C+L-band).

[0012] Therefore, there is interest in improving the performance of coherent OPMs to efficiently monitor the optical properties of multiple optical signals propagating in DWDM optical transmission and switching systems. Summary of the Invention

[0013] The embodiments of this disclosure have been developed based on the developer’s understanding of the drawbacks associated with the prior art, namely, to operate the coherent optical performance monitor (OPM) in an efficient manner in order to reduce the time required to monitor channel performance, such as monitoring the signal power propagating in the channel.

[0014] According to a first broad aspect of this disclosure, an optical performance monitor (OPM) is provided, comprising: an input port for receiving an optical channel signal, wherein the optical channel signal is superimposed with a pilot tone (PT) signal; a local oscillator (LO) including a tunable laser for operating in a coarse scan mode and a fine scan mode, and generating different LO signals depending on the mode in which the LO operates; at least one optical coupler for merging the optical channel signal with at least one LO signal generated by the LO to generate a merged optical signal; at least one photodetector for detecting the merged optical signal and converting the detected merged optical signal into an electrical signal; at least one amplifier for amplifying the electrical signal; and at least one analog-to-digital converter (ADC). A converter (ADC) is used to convert an amplified electrical signal into a digital signal; a digital signal processor is used to process the digital signal, extract channel-specific information included in the PT signal, and calculate the channel power based on the channel-specific information; and a controller is used to control the frequency step size of the LO and maintain a management table, wherein the management table includes flags associated with different coarse scan indices (C-indexes) and information associated with different channels, wherein the C-indexes represent the frequency slots in which the LO signal is generated when the LO operates in coarse scan mode.

[0015] According to any other aspect of this disclosure, the OPM has a larger frequency step size in coarse scan mode compared to the frequency step size of the LO operating in fine scan mode.

[0016] According to any other aspect of this disclosure, the OPM wherein: the channel power calculated by the digital signal processor when the LO operates in the coarse scan mode is an approximate channel power, and the channel power calculated by the digital signal processor when the LO operates in the fine scan mode is an integrated channel power.

[0017] According to any other aspect of this disclosure, the OPM, wherein the digital signal processor calculates a power scaling factor based on the approximate channel power and the integrated channel power.

[0018] According to any other aspect of this disclosure, the OPM, wherein the digital signal processor corrects the approximate channel power based on the power scaling factor.

[0019] According to any other aspect of this disclosure, the OPM, wherein the LO operates more frequently in the coarse scan mode compared to the fine scan mode.

[0020] According to any other aspect of this disclosure, the OPM, wherein the flags in the management table include signal flags and PT signal reception flags.

[0021] According to any other aspect of this disclosure, the OPM is wherein: if a combined optical signal is detected at the C-index and the amplitude of the detected signal is higher than a certain threshold, the signal flag corresponding to the C-index is set to "Y"; and if no signal is detected at the C-index, or if a combined optical signal is detected at the C-index and the amplitude of the detected signal is lower than a certain threshold, the signal flag corresponding to the C-index is set to "N".

[0022] According to any other aspect of this disclosure, the OPM is wherein: if the channel-specific information is extracted from the digital signal corresponding to the detected optical signal at the C-index, the PT signal reception flag corresponding to the C-index is set to "Y"; and if the channel-specific information has not yet been extracted from the digital signal corresponding to the detected optical signal at the C-index, the PT signal reception flag corresponding to the C-index is set to "N".

[0023] According to any other aspect of this disclosure, in the OPM, if the signal flag corresponding to the C-index is set to "Y" and the PT signal reception flag corresponding to the C-index is set to "N", the controller is configured to prioritize the extraction of the channel-specific information by instructing the LO to generate an LO signal associated with the C-index.

[0024] According to any other aspect of this disclosure, the OPM, wherein: the information associated with different channels in the management table includes entries corresponding to channel association, channel C-index, and fine scan flag; the channel association represents a C-index associated with a channel, the channel C-index represents a C-index selected from the C-index associated with a channel, and the fine scan flag represents the status of whether a fine scan has been performed or not with respect to the channel.

[0025] According to any other aspect of this disclosure, the C-index associated with the channel is determined by the channel-specific information.

[0026] According to any other aspect of this disclosure, the fine scan flag is set to "Y" if the integrated channel power associated with the channel is calculated, and otherwise the scan flag is set to "N".

[0027] According to any other aspect of this disclosure, the frequency step size of the LO operating in coarse scan mode is further reduced based on the selected C-index.

[0028] According to any other aspect of this disclosure, the OPM, if a channel is removed, is further configured to update the management table by causing the LO to operate in coarse scan mode.

[0029] According to any other aspect of this disclosure, the OPM, wherein the PT signal comprises PT frames, and each PT frame comprises all PT information.

[0030] According to any other aspect of this disclosure, the OPM includes sub-PT frames, and each sub-PT frame includes a portion of the PT signal, the portion of the PT signal including channel spectral range information for facilitating coarse and fine scanning.

[0031] According to a second broad aspect of this disclosure, a method for monitoring optical performance is provided, comprising: receiving an optical channel signal, wherein the optical channel signal is superimposed with a tuning peak (PT) signal; operating a local oscillator (LO) including a tunable laser in a coarse scan mode and a fine scan mode, and generating different LO signals according to the mode in which the LO operates; merging the optical channel signal with at least one LO signal generated by the LO to generate a merged optical signal; detecting the merged optical signal and converting the merged optical signal into an electrical signal; amplifying the electrical signal; converting the amplified electrical signal into a digital signal; processing the digital signal and extracting channel-specific information included in the PT signal; calculating channel power based on the channel-specific information; and maintaining a management table, wherein the management table includes flags associated with different coarse scan indices (C-indices) and information associated with different channels, wherein the C-indices represent the frequency slot in which the LO generates the LO signal when operating in the coarse scan mode.

[0032] The method according to any other aspect of this disclosure, wherein the frequency step size of the LO operating in coarse scan mode is larger than the frequency step size of the LO operating in fine scan mode.

[0033] The method according to any other aspect of this disclosure, wherein: the channel power calculated when the LO operates in the coarse scan mode is an approximate channel power, and the channel power calculated when the LO operates in the fine scan mode is an integrated channel power.

[0034] The method described according to any other aspect of this disclosure further includes calculating a power scaling factor based on the approximate channel power and the integrated channel power.

[0035] The method according to any other aspect of this disclosure, wherein the approximate channel power is corrected based on the power scaling factor.

[0036] The method according to any other aspect of this disclosure, wherein the LO operates more frequently in the coarse scan mode compared to the fine scan mode. Attached Figure Description

[0037] Other features and advantages of this disclosure will become apparent from the following detailed description, taken in conjunction with the accompanying drawings. In the drawings:

[0038] Figure 1 (Prior Art) depicts a block diagram of an optical network based on a dense wavelength division multiplexing (DWDM) optical transmission and switching system;

[0039] Figure 2 (Prior Art) shows more details of the link between two nodes in an optical network;

[0040] Figure 3A (Prior Art) shows a representative spectrum of the optical channel signal under test;

[0041] Figure 3B (Prior Art) shows a representative optical channel signal 252 with an amplitude-modulated PT signal;

[0042] Figure 4A (Prior Art) shows a conventional coherent optical performance monitor (OPM) based on single polarization;

[0043] Figure 4B (Prior Art) illustrates a conventional coherent OPM based on dual polarization;

[0044] Figure 5 The following are examples of coherent OPMs included in optical networks according to various embodiments of the present disclosure;

[0045] Figure 6A Examples of coarse scans according to various embodiments of this disclosure are shown;

[0046] Figure 6B Various embodiments of this disclosure are shown with frequency step size Δf c A general example of a coarse scan performed;

[0047] Figure 7A PT signal frames according to various embodiments of the present disclosure are shown;

[0048] Figure 7B Another example of a PT signal frame according to various embodiments of the present disclosure is shown;

[0049] Figure 8 Management tables created and maintained by a controller according to various embodiments of this disclosure are shown;

[0050] Figure 9 A high-level block diagram depicting exemplary components of a controller according to various embodiments of the present disclosure; and

[0051] Figure 10 A flowchart depicts the processing corresponding to various embodiments of the present disclosure and a method for monitoring optical performance implemented on a coherent OPM.

[0052] It should be understood that in all the drawings and corresponding descriptions, the same features are identified by the same reference numerals. Furthermore, it should be understood that the drawings and the following description are for illustrative purposes only, and such disclosure does not limit the scope of the claims. Detailed Implementation

[0053] This disclosure aims to address at least some of the deficiencies of the prior art; in particular, this disclosure describes systems and methods for monitoring optical performance.

[0054] Unless otherwise defined or indicated by the context, all technical and scientific terms used herein have the same meaning as those commonly known to one of ordinary skill in the art to which the described embodiments pertain.

[0055] In the context of this specification, a "controller" is any computer hardware capable of running software suitable for the relevant task at hand. In the context of this specification, the term "client device" is generally associated with a user of the client device. Therefore, some (non-limiting) examples of client devices include personal computers (desktops, laptops, netbooks, etc.), smartphones and tablets, as well as network devices such as routers, switches, and gateways. It should be noted that a device acting as a client device in this context does not exclude the possibility of it acting as a server for other client devices. The use of the term "client device" does not preclude the use of multiple client devices to receive / send, perform, or cause the performance of any task or request, or the result of any task or request, or the steps of any method described herein.

[0056] In the context of this specification, unless otherwise expressly stated, the terms “first,” “second,” “third,” etc., are used as adjectives solely to distinguish between the nouns they modify, and not to describe any particular relationship between those nouns. Therefore, for example, it should be understood that the use of the terms “first processor” and “third processor” is not intended to imply, for example, any particular order, type, chronological order, hierarchy, or ranking of servers / servers, nor is their use intended to imply that any “second server” must exist in any given situation. Furthermore, as discussed in other contexts herein, references to the elements “first” and “second” do not preclude the two elements from being the same actual real-world element. Thus, for example, in some cases, a “first” server and a “second” server may be the same software and / or hardware; in others, they may be different software and / or hardware.

[0057] It should be understood that when an element is referred to as “connected” or “coupled” to another element, it may be directly or indirectly connected or coupled to the other element or any intervening elements that may exist. Conversely, when an element is referred to as “directly connected” or “directly coupled” to another element, there are no intervening elements. Other terms used to describe the relationship between elements should be interpreted in a similar manner (e.g., “between” vs. “directly between”, “adjacent” vs. “directly adjacent”, etc.).

[0058] In the context of this specification, when an element is referred to as being “associated” with another element, in some embodiments the two elements may be directly or indirectly associated, related, connected, coupled, the second element may use the first element, etc., without limiting the scope of this disclosure.

[0059] The terminology used herein is intended only to describe specific, representative embodiments and is not intended to limit the technology. Unless the context clearly states otherwise, the singular forms “a,” “an,” and “the” used herein are intended to include the plural forms. It should also be understood that the terms “comprises” and / or “comprising” as used herein are used to indicate the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0060] Each implementation of this technology has at least one of the above-described objectives and / or aspects, but not necessarily all of them. It should be understood that some aspects of this technology, developed in an attempt to achieve the above objectives, may not satisfy those objectives, and / or may satisfy other objectives not specifically described herein.

[0061] The examples and conditions described herein are primarily intended to help the reader understand the principles of this technology, rather than to limit its scope to these specific examples and conditions. It should be understood that those skilled in the art can design various arrangements, which, although not explicitly described or shown herein, embody the principles of this technology and are included within its spirit and scope.

[0062] Furthermore, for ease of understanding, the following description illustrates a relatively simplified implementation of this technology. Those skilled in the art will understand that various implementations of this technology can be far more complex.

[0063] In some cases, examples that are considered beneficial modifications to the present technology may be illustrated. This is merely to aid understanding and is not intended to define the scope or limits of the present technology. These modifications are not an exhaustive list, and those skilled in the art can make other modifications while still remaining within the scope of the present technology. Furthermore, the absence of examples of modifications should not be construed as meaning that modifications are impossible and / or that the described content is the only way to implement the elements of the present technology.

[0064] Furthermore, all descriptions and specific examples of the principles, aspects, and implementations of this technology herein are intended to include their structural and functional equivalents, whether they are currently known or will be developed in the future. Therefore, for example, those skilled in the art will understand that any block diagram herein represents a conceptual view of an illustrative circuit embodying the principles of this technology. Similarly, it should be understood that any flowchart, diagrammatic flowchart, state transition diagram, pseudocode, etc., represents various processes that can be substantially represented in a computer-readable medium and thus executed by a computer or processor, whether or not such computer or processor is explicitly shown.

[0065] The functionality of the various elements shown in the diagram, including any functional blocks labeled "processor" or "processing unit," can be provided using dedicated hardware and hardware capable of executing software associated with appropriate software. When provided by a processor, these functions can be provided by a single dedicated processor, a single shared processor, or multiple separate processors, some of which may be shared. In some embodiments of this technology, the processor can be a general-purpose processor, such as a central processing unit (CPU), or a purpose-specific processor, such as a graphics processing unit (GPU). Furthermore, the explicit use of the terms "processor" or "controller" should not be construed as specifically referring to hardware capable of executing software, and may implicitly include, but is not limited to, digital signal processor (DSP) hardware, network processors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), read-only memory (ROM), random access memory (RAM), and non-volatile memory for storing software. Other conventional and / or custom hardware may also be included.

[0066] A software module, or a module or unit implied as software, may be represented herein as a flowchart element or any combination of other elements and / or textual descriptions indicating the execution of process steps. Such modules may be executed by hardware, whether explicitly or implicitly shown.

[0067] Based on these fundamental principles, this disclosure aims to address at least some of the shortcomings of current technologies. Specifically, this disclosure describes systems and methods for monitoring optical performance.

[0068] Referring to the accompanying drawings, Figure 1 (Prior Art) depicts a block diagram of an optical network 100 based on a dense wavelength division multiplexing (DWDM) optical transmission and switching system. The optical network 100 typically has multiple nodes 102-1, 102-2…102-7. Each node (e.g., 102-1, 102-2…102-7) may include an optical multiplexing section (OMS), which includes an optical add-drop multiplexer, such as a reconfigurable optical add-drop multiplexer (ROADM). Each reconfigurable OADM includes at least one wavelength selective switch (WSS), a multiplexer, and a demultiplexer. Each node (e.g., 102-1, 102-2…102-7) can be used to add, delete, and / or reroute wavelengths. Each OMS-based node may also include multiple optical transport sections (OTS), where the wavelength remains the same across all OTSs.

[0069] Each node in the optical network 100 (e.g., 102-1, 102-2...102-7) may also be combined with one or more laser sources for generating, emitting, or radiating light pulses with a certain pulse duration. It is also conceivable that the emitted light may be single-polarized, double-polarized, or randomly polarized, and may have a specific polarization (e.g., linear, elliptical, or circular polarization) depending on the signal format.

[0070] Furthermore, each node in the optical network 100 (e.g., 102-1, 102-2…102-7) can be combined with multiple optical amplifiers, such as erbium-doped fiber amplifiers (EDFAs), to amplify the optical signal. The optical network 100 may also employ one or more optical network elements and modules (which may include any or both active and passive elements / modules), such as optical filters, WSSs, arrayed waveguide gratings, optical transmitters, optical receivers, processors, and other suitable components. However, for simplicity and ease of handling, these elements have been omitted from Figure 1.

[0071] It is conceivable that nodes in an optical network can be communicatively connected via links comprising multiple optical fibers. The optical fibers can be of any suitable type, such as single-mode fiber, multimode fiber, standard single-mode fiber (SSMF), large effective area fiber (LEAF), etc. The link also includes multiple optical amplifiers, such as EDFAs. The link between two nodes (e.g., 102-1 and 102-2) also includes optical amplifiers.

[0072] The optical network devices described herein include one or more passive and / or active optical network components and / or modules of optical network 100, including but not limited to optical fibers, optical amplifiers, optical filters, optical links, WSS, arrayed waveguide gratings, and laser sources.

[0073] Nodes within the optical network 100 (e.g., 102-1, 102-2…102-7) typically transmit signals on one of multiple optical wavelength channels. Throughout this disclosure, the term "wavelength channel" refers to a modulated optical signal at a specific wavelength. A wavelength channel is also referred to herein as a "channel." Each channel is characterized by its channel bandwidth and channel center frequency, typically defined by a frequency grid.

[0074] As described herein, the term "transmitted optical channel signal" refers to the optical channel signal before it is propagated through the optical network equipment. As described herein, the term "received optical channel signal" refers to the optical channel signal after it has been propagated through the optical network equipment.

[0075] In the optical network 100, an amplitude modulation (AM) signal can be used to monitor channel power. The "AM signal" (also referred to herein as a "PT signal") is a low-frequency (e.g., kHz to MHz) modulation of the intensity of the modulation applied to the optical channel signal. The PT signal may include one or more frequencies. The spectral characteristics of the PT signal should not limit the scope of this disclosure.

[0076] The modulation depth of PT signals is typically small (e.g., a few percent of the channel power). PT signals provide an in-band auxiliary channel for performance monitoring.

[0077] Each channel can be modulated with a different PT signal. For example, different modulation frequencies can be applied to different channels. Different spreading sequences can also be applied to spectrally spread PT signals. Therefore, the power of a specific PT signal can be used to indicate the power of the optical channel signal in a wavelength division multiplexed (WDM) system. The PT signal can be further modulated to carry channel characterization information.

[0078] Figure 2 (Prior Art) illustrates further details of the link 200 between two nodes 102-1 and 102-2 of optical network 100. Nodes 102-1 and 102-2 may include a ROADM 202, an optical amplifier 204, a coherent transmitter 206, a coherent receiver 208, and a coherent OPM 210, as well as other components (not shown). The two nodes 102-1 and 102-2 can be connected via optical fiber 212. Node 102-1 can receive one or more DWDM signals 214, 216, discard one or more channels from the DWDM signals 214, 216 at receiver 208, add one or more channels generated by transmitter 206, and pass through other channels. Signals can be added or discarded using a WSS or a combination of WSS and other multiplexer and demultiplexer components (not shown). In some cases, discarded channels are converted from the optical domain to the electrical domain, and added channels are converted from the electrical domain to the optical domain. Otherwise, channels are switched or passed through in the optical domain.

[0079] Figure 3A (Prior Art) shows a representative spectrum of the optical channel signal 252 under test. A local oscillator (LO) can be used to measure the power across the entire spectrum via a coherent OPM. In this way, the wavelength / frequency of the LO can be precisely tuned. The shaded area shows the electrical bandwidth of the detection circuit, which determines the resolution bandwidth of the coherent OPM used to monitor the optical channel performance.

[0080] For performance optimization and other operational / maintenance purposes, various optical networks (such as optical network 100) require a variety of information, such as the power of each channel, channel-specific information (center wavelength, modulation format, baud rate, spectral shape, source / destination, etc.). For this purpose, some optical networks (such as optical network 100) rely on pitch modulation (PT) technology.

[0081] There are many different types of PT signals. The most common is amplitude-modulated PT (for simplicity, referred to as AM-PT or PT). Transmitter 206 can apply small, relatively low-frequency (kHz / MHz) amplitude / intensity modulation to the optical signal (GHz). A unique low-frequency PT signal can be applied to each optical signal. To detect the PT signal, at least one photodetector can be used to detect all optical channel signals without optical demultiplexing. By performing spectral analysis in the electrical domain or equivalent digital domain, the presence and power of all channels can be monitored simultaneously. This provides a low-cost monitoring solution. The PT signal can be further turned on and off to carry channel-specific information. Figure 3B (prior art) shows a representative optical channel signal 252 with an amplitude-modulated PT signal 254.

[0082] It should be noted that in some cases, the optical channel signal may have single polarization, while in others it may have dual polarization. If the optical channel signal has single polarization, the optical network 100 can rely on a conventional coherent OPM 300 (as shown in Figure 4A (prior art)) or a conventional coherent OPM 400 (as shown in Figure 4B (prior art)) to monitor channel performance. However, if the optical channel signal has dual polarization, the optical network 100 can rely on a conventional coherent OPM 400 (as shown in Figure 4B (prior art)) to monitor channel performance.

[0083] As shown in Figure 4A, the test optical channel signal with single polarization and the local oscillator (LO) signal generated by the local oscillator (LO) 302, which includes a tunable laser, are combined by coupler 304. A balanced photodetector (BPD) 306 converts the output of coupler 304 into an electrical signal, which is amplified by an amplifier such as a transimpedance amplifier (TIA) 308, and optionally by an additional amplifier. The amplified electrical signal is then converted into a digital signal by an analog-to-digital converter (ADC) 310. The digital signal is processed by a digital signal processor (DSP) 312. In some cases, processing can also be performed in the analog domain.

[0084] Figure 4B illustrates a conventional coherent OPM 400 operating on a dual-polarized optical channel signal under test. The main difference between the conventional coherent OPM 300 and the conventional coherent OPM 400 is that in the latter, the dual-polarized optical channel signal under test is split into two orthogonally polarized optical channel signals by polarization beam splitters (PBS) 404-1 and 404-2. These two orthogonally polarized optical channel signals are then processed by couplers 406-1 and 406-2, BPD 408-1 and BPD 408-2, TIA 410-1 and TIA 410-2, ADC 412-1 and ADC 412-2, and DSP 414, respectively.

[0085] It should be noted that while the LO 302 and LO 402 in the conventional coherent OPM 300 and conventional coherent OPM 400 operate with small step sizes as small as 0.1 GHz or less, thus providing very good spectral resolution, such step sizes require a large number of samples and longer measurement times (on the order of one second) for scanning (scanning the entire frequency range, typically C-band, L-band, or C+L-band). However, when monitoring optical performance, faster scan speeds (less than 0.1 seconds) are required.

[0086] Furthermore, traditional PT techniques require simultaneous and continuous detection of all channels. However, conventional coherent OPM 300 and OPM 400 monitor only one spectral component at any given time. Therefore, there is interest in developing a coherent OPM that offers faster scan speeds and is effectively compatible with PT techniques.

[0087] As mentioned above, Figure 5 A coherent OPM 500 included in an optical network 100 according to an embodiment of the present disclosure is illustrated. As shown, the coherent OPM 500 includes an LO 502, PBS 504-1 and PBS 504-2, couplers 506-1 and 506-2, BPD 508-1 and BPD 508-2, TIA 510-1 and TIA 510-2, ADC 512-1 and ADC 512-2, DSP 514, and controller 516. It should be noted that the coherent OPM 500 may include other components and modules. However, for simplicity, these components and modules have been described from... Figure 5 Omitted in .

[0088] It has been observed that the channel spectrum is relatively stable, and the channel power can be derived from a small portion of the signal channel spectrum. Therefore, the controller 516 can be used to control and configure various components of the coherent OPM 500 to perform coarse scanning, PT signal reception (which may include the extraction of channel-specific information), and fine scanning.

[0089] The LO 502 may include a tunable laser and can be used to operate in coarse scan and fine scan modes to generate different LO signals. For a given spectral bandwidth, the frequency step size at which the LO 502 generates different LO signals may depend on the mode in which the LO 502 operates. For example, for a 5 THz spectral bandwidth, if the LO 502 operates in coarse scan mode, the generated LO signal may have a frequency step size of 25 GHz (i.e., two optical signals separated by a 25 GHz frequency difference). On the other hand, for a 5 THz spectral bandwidth, if the LO 502 operates in fine scan mode, the generated LO signal may have a frequency step size of 0.1 GHz (i.e., two optical signals separated by a 0.1 GHz frequency difference). The frequency step size of the LO 502 operating in coarse scan mode is larger than that of the LO 502 operating in fine scan mode.

[0090] It should be noted that in some embodiments, the controller 516 can control the operating mode of the LO 502 and can control the frequency step size at which the LO 502 can generate the LO signal.

[0091] The controller 516 can control the operation of the LO 502 in such a way that, during coarse scanning, the LO 502 can generate an optical LO signal with a larger frequency difference (i.e., a larger frequency step size).

[0092] In modern DWDM fiber optic communication systems, the baud rate of the optical channel signal is primarily greater than 25 Gb. For example, for 100 Gbps QPSK, the optical channel signal requires a baud rate of approximately 34 Gb. Therefore, a frequency step size of 25 GHz ensures that each channel has at least one coarse optical signal, and that no channel is missed during the coarse scan.

[0093] When no channel information is available for the coherent OPM 500, the fixed frequency step size described above can be used during the initial coarse scan. Once channel information, such as baud rate, bandwidth of each channel, or similar operating parameters (discussed below), has been extracted, the frequency step size can be changed as needed.

[0094] When the baud rate is greater than the assumed baud rate (e.g., 34Gb), the frequency step size can be increased to cover at least one spectral location in each channel. On the other hand, if the baud rate is less than the assumed baud rate (e.g., 34Gb), the frequency step size can be decreased to further increase the speed.

[0095] Figure 6A Example 550 of a coarse scan according to various embodiments of the present disclosure is shown. C1, C2...C n As a coarse scan index known as the C-index, the C-index can represent the frequency slots at which the LO 502 can generate the LO signal when operating in coarse scan mode. For example, the entire spectrum range to be measured is divided into 200 frequency slots. It is assumed that the spectral width of each channel (e.g., CH-1, CH-2, CH-3…CH-n) is greater than a frequency step size of 25 GHz. It is important to note that it is not necessary to perform measurements at multiple frequency slots for a given channel. To reduce the number of measurements, the controller 516 can select one of a plurality of C-indexes to represent the channel. When selecting a C-index for a given channel, the power at the C-index must be greater than a threshold to ensure that it is a signal channel and not background noise.

[0096] It should be noted that, according to the various embodiments of this disclosure, the 25 GHz frequency step size is discussed only as a non-limiting example, and any other suitable larger or smaller step size may be selected by the controller 516 according to the requirements of the optical network 100. Figure 6B An embodiment of the present disclosure is shown with a frequency step size Δf c Example 560 of a coarse scan performed.

[0097] Back Figure 5The coherent OPM 500 may include an input port (not shown for simplicity) to receive an optical channel signal whose performance needs to be monitored. The optical channel signal may be superimposed with a PT signal. It is assumed that the optical channel signal has dual polarization; however, the optical channel signal can have any direction, and the coherent OPM 500 may have corresponding components.

[0098] As described above, in some embodiments, the optical channel signal is split into two sets of orthogonally polarized optical channel signals by PBS 504-1. The first set of orthogonally polarized optical channel signals can be forwarded to coupler 506-1, and the second set of orthogonally polarized optical channel signals can be forwarded to coupler 506-2.

[0099] As previously described, the optical channel signal can be amplitude modulated using the desired PT signal. In some embodiments, transmitter 206 can be used to modulate the amplitude of the optical channel signal with the PT signal. In some examples, transmitter 206 can encode the PT signal before amplitude modulation. It should be noted that how transmitter 206 encodes and / or modulates the optical channel signal should not limit the scope of this disclosure.

[0100] In a non-limiting embodiment, transmitter 206 can receive a data bitstream including bit values ​​1 and 0. The data stream may include channel-specific information such as center wavelength, modulation format, baud rate, spectral shape, source / destination, etc. Transmitter 206 can convert the data bitstream into an encoded data stream and encode the PT signal with the encoded data stream to generate an encoded PT signal. Further, transmitter 206 can use the encoded PT signal to modulate the amplitude of the optical channel signal. The steps of receiving, converting, encoding, and modulating can be performed by an encoder included in transmitter 206.

[0101] Figure 7A A PT signal frame 570 according to various embodiments of the present disclosure is shown. As shown, only a small time window is available for PT detection, which imposes certain requirements on the PT data structure. PT data is typically static and the amount of data to be carried is usually small (e.g., a few hundred bits). In one embodiment, transmitter 206 may place all PT information in a single PT frame and repeatedly transmit that PT frame with the same data. To recover the PT data, the duration T of the PT frame is measured. M It can be greater than the duration T of the PT frame. Frame .

[0102] In another embodiment, such as Figure 7BAs shown, PT data can be transmitted over multiple repeating sub-PT frames 580. Each sub-PT frame 580 may include channel spectrum range information to facilitate coarse and fine scanning. Other less urgent information may be transmitted over the multiple sub-PT frames 580. The channel spectrum range information can be obtained by detecting any one of the sub-PT frames.

[0103] It should be noted that each transmitter 206 can transmit its own PT signal. In a link between two nodes (e.g., 102-1, 102-2, etc.) with multiple optical channel signals, PT frames from different channels may be out of sync. Frame / subframe timing may be difficult to determine in advance; however, the cyclic / quasi-cyclic nature of PT frames can provide an effective means of associating PT frames with the associated transmitter 206.

[0104] Back Figure 5 LO 502 can generate intervals Δf between each other. c The LO signal. Δf c The value can be provided by controller 516. For example, if the channel operating frequency range is 191THz to 196THz, LO 502 can generate LO signals at 191.025THz, 191.050THz, 191.075THz, etc. However, LO 502 can remain at a specific frequency until a PT signal is detected. LO 502 can forward the LO signal to PBS 504-2 to generate two orthogonally polarized LO signals. The first orthogonally polarized LO signal can be forwarded to coupler 506-1, and the second orthogonally polarized LO signal can be forwarded to coupler 506-2.

[0105] Couplers 506-1 and 506-2 can combine orthogonally polarized optical channel signals with orthogonally polarized LO signals to generate a combined optical signal. The combined optical signal can represent the spectral components extracted from the orthogonally polarized optical channel signals located at the frequencies of the orthogonally polarized LO signals.

[0106] BPD 508-1 and BPD 506 can convert the outputs (i.e., combined optical signals) of couplers 506-1 and 506-2 into electrical signals. Once the spectral components extracted from the orthogonally polarized optical channel signal have been converted into electrical signals, LO 502 can generate the next LO signal to extract other spectral components.

[0107] BPD 508-1 and BPD 508-2 can transmit electrical signals to TIA 510-1 and TIA 510-2. TIA 510-1 and TIA 510-2 can amplify the electrical signals, apply low-pass filtering, and forward the amplified electrical signals to ADC 512-1 and ADC 512-2. In some embodiments, there may be an additional electrical amplifier after TIA 510-1 and TIA 510-2 (omitted for simplicity). ADC 512-1 and ADC 512-2 can convert the amplified electrical signals into digital signals and forward the digital signals to DSP 514.

[0108] The DSP 514 can be used to process digital signals. Thus, the DSP 514 can extract the PT signal and decode channel-specific information from the PT signal, such as center frequency, modulation format, baud rate, spectral shape, spectral information, source / destination, etc. It should be noted that how the DSP 514 extracts the PT signal and decodes the channel-specific information should not limit the scope of this disclosure.

[0109] The DSP 514 can use channel-specific information to determine which C-indexes the channel covers. For example, ... Figure 6A As shown, the first channel CH-1 includes C-indices C1 and C2, and the second channel CH-2 includes C-indices C4, C5, and C7, etc. The DSP 514 can provide this information to the controller 514. The DSP 514 can be used to calculate the power of each channel using the channel-specific information.

[0110] In some embodiments, controller 514 can create and maintain, such as Figure 8 The management table 600 shown is from various embodiments of this disclosure. For each C-index, the management table 600 may maintain association flags and information associated with different channels, such as signal flags, PT signal reception flags, channel associations, channel C-indexes, and fine scan flags (details of fine scan will be discussed later in the disclosure). It should be noted that the management table 600 may include additional entries associated with other flags and information, but these additional entries have been omitted for simplicity.

[0111] When DSP 514 detects a combined optical signal in a specific frequency slot associated with C-index, the signal flag corresponding to C-index can be set to "Y". For example, if DSP 514 detects a combined optical signal in a frequency slot (e.g., 191.050 THz) associated with C-index C2, and the power of the detected signal is higher than a specific threshold, then the signal flag for C-index C2 can be set to "Y". Furthermore, when DSP 514 does not detect a signal in a specific frequency slot associated with C-index, or the power of the detected signal is lower than a specific threshold, the signal flag corresponding to C-index can be set to "N". For example, if DSP 514 does not detect a signal in a frequency slot (e.g., 191.175 THz) associated with C-index C7, and / or the power of the detected signal is lower than a specific threshold, then the signal flag for C-index C7 can be set to "N".

[0112] If the channel-specific information in the PT signal associated with the signal detected by the DSP has been extracted by the DSP 514, the PT signal reception flag corresponding to the C-index can be set to "Y". If the DSP 514 cannot extract the channel-specific information in the PT signal (e.g., when initiating coherent OPM 500 and / or adding a channel via one or more ROADM 202s), the PT signal reception flag corresponding to the C-index can be set to "N". The DSP 514 may not be able to extract the channel-specific information in the PT signals of all channels in one PT signal reception cycle. If the PT signal reception flag is set to "N" for a C-index with the signal flag set to "Y", the controller 516 can prioritize the extraction of channel-specific information by instructing the LO to generate an LO signal associated with the C-index.

[0113] Channel association can be based on channel-specific information extracted from PT signals to represent channels and associated C-indices. For example, C-indices C2 and C3 can correspond to channel CH-1, C-indices C4, C5, and C6 can correspond to channel CH-2, and so on.

[0114] As discussed earlier, for a specific channel, a single PT signal detection should be sufficient to extract channel-specific information. For a channel in which more than one signal sample has been detected, such as channel CH-1, where signals have already been detected in the bands corresponding to C-indices C2 and C3, controller 516 can specify in management table 600 which C-index can be used for PT signal detection for subsequent processing. The channel C-index can represent a C-index selected from the C-indexes associated with a specific channel for subsequent processing during coarse scanning. For example, C-index C2 can represent channel CH-1, C-index C5 can represent channel CH-2, and so on. The channel C-index associated with a channel is determined based on channel-specific information.

[0115] In the event of channel removal, the C-index can change from having a signal (signal flag set to Y) to not having a signal (signal flag set to N), and its associated PT signal reception flag, channel C-index, and other entries can be removed by controller 516. Furthermore, LO 502 can be used to operate again in coarse scan mode.

[0116] The management table 600 can be populated immediately when associated information is available and can be refreshed periodically by the controller 516. In some embodiments, during normal operation, the management table 600 is populated with all entries and can be refreshed for all channels with the same priority. In other embodiments, depending on system requirements, the refreshing of some entries may take precedence over other entries.

[0117] Once the management table 600 is populated with the channel C-index entry and associated channel-specific information, the DSP 514 can be used to calculate the approximate channel power using the power associated with the PT signal of a specific channel. The DSP 514 can calculate the approximate channel power when the LO 502 operates in coarse scan mode. At least one signal sample from the channel can be used to calculate the approximate channel power.

[0118] After performing a coarse scan and filling the entries in management table 600 for at least one cycle (i.e., traversing all optical channel signals at least once), the coherent OPM 500 can perform a fine scan. During the fine scan, the controller 516 can change the step size of LO 502 and can perform scanning of the optical channel signals in steps smaller than those associated with the coarse scan (e.g., on the order of 0.1 GHz, 0.5 GHz, etc.).

[0119] It should be noted that, apart from the fact that LO 502 is used to operate with a smaller frequency step size, other components of the coherent OPM 500 can perform functions similar to those used when performing a coarse scan. In one embodiment, controller 516 can provide a fine frequency step size to LO 502. LO 502 can generate an LO signal based on this fine frequency step size. Couplers 506-1 and 506-2, BPD 508-1 and BPD 508-2, TIA 510-1 and TIA 510-2, ADC 512-1 and ADC 512-2, and DSP 514 can be used to operate in a manner similar to that discussed above.

[0120] The DSP 514 can calculate the integrated channel power associated with different channels based on channel-specific information such as the spectral range extracted from the PT signal. The DSP 514 can calculate the integrated channel power when the LO 502 operates in fine-scan mode. In some embodiments, the integrated channel power can be calculated by integrating the power associated with samples collected during a fine scan of the spectrum associated with the channel. The spectral information can be obtained from the associated channel-specific information. The integrated channel power can be calculated using multiple signal samples from the channel.

[0121] The controller 516 can update the fine scan flag in the management table 600. When the integrated channel power associated with a channel (e.g., CH-1) is calculated, the value of the fine scan flag corresponding to that channel can be set to "Y". Otherwise, the value of the fine scan flag corresponding to that channel can be set to "N".

[0122] The DSP 514 can calculate a power scaling factor based on the approximate channel power value and the integrated channel power value. The power scaling factor can represent a factor by which the approximate channel power should be increased or decreased to make it equal to each fine power channel value. In some embodiments, without limiting the scope of this disclosure, the power scaling factor can be calculated by taking the ratio of the approximate channel power value to the integrated channel power value.

[0123] After calculating the integrated channel power for different channels, the coherent OPM 500 can be used to operate in coarse scan mode and continue to monitor the channel power by using channel-specific information extracted from the PT signal and then using a power scaling factor to correct (e.g., increase, decrease, or not change) the calculated approximate channel power.

[0124] Management Table 600 plays a crucial role in improving the performance of the Coherent OPM 500. Some non-limiting examples of how the Coherent OPM 500 utilizes Management Table 600 are discussed in the following disclosures.

[0125] In some embodiments, the controller 516 can determine which channel to monitor in the next cycle based on the PT signal reception flag. For example, if C-index C 10 If the signal flag has been set to "Y", but the corresponding PT signal reception flag has been set to "N", then controller 516 can instruct LO 502 to tune to the C-index C. 10 The associated frequencies. Thus, the coherent OPM 500 can operate to extract frequencies related to the C-index C. 10 Channel-specific information of the associated channel.

[0126] The coherent OPM 500 can calculate approximate channel power for different channels using their respective channel-specific information. Since the approximate channel power calculation is based on a large frequency step size of LO 502, the scan time to traverse all optical channel signals can be very short compared to conventional OPMs (such as OPM 300 and OPM400).

[0127] To further reduce the frequency step size during the coarse scan, controller 516 can use the channel association entry in management table 600 to select a C-index for each channel. After the first cycle, controller 516 can provide only the frequency component associated with the selected C-index, thereby further reducing the frequency step size and improving operating speed.

[0128] As discussed earlier, the coherent OPM 500 can also be used to perform fine scans. The purpose of fine scanning is to calculate the integrated channel power that is closer to the actual channel power. It is important to note that, unlike in conventional OPMs (such as OPM 300 and OPM 400) where fine scans are performed continuously on all channels, in the coherent OPM 500, fine scans can be performed locally and infrequently. That is, the LO 502 operates in coarse scan mode more frequently than the LO 502 operates in fine scan mode.

[0129] For example, if controller 516 observes that the PT signal reception flag has been synchronized with the signal flag and that the approximate channel power has been calculated, controller 516 can instruct LO 502 to operate with large step sizes. In some embodiments, controller 516 may also provide a frequency range associated with one or more channels for fine scanning. For example, controller 516 may provide the frequency components associated with channel CH-1 extracted from the PT signal. Coherent OPM 500 can perform fine scanning on channel CH-1, and DSP 514 can calculate the fine power of channel CH-1. Controller 600 can update management table 600 by setting the fine scan flag associated with channel CH-1 to 'Y'.

[0130] The DSP 514 can also use the approximate channel power and the integrated channel power of channel CH-1 to calculate the power scaling factor. For subsequent scans, unless there are changes in channel CH-1 (e.g., increased or decreased signal, greater power loss in the channel, etc.), the coherent OPM 500 can rely on the approximate channel power and the power scaling factor to determine the power associated with channel CH-1.

[0131] It should be noted that the techniques discussed above are applicable to all channels. The Coherent OPM 500 can calculate the integrated channel power for different channels in different periods. For most periods, the Coherent OPM 500 can operate in coarse scan mode, thereby improving the operating speed of the Coherent OPM 500.

[0132] Furthermore, the coherent DSP 514 can be used to combine different integrated channel powers from different channels to generate a fine spectrum across the entire measurement spectrum band.

[0133] Optical performance monitoring via the Coherent OPM 500 can include: ensuring proper switching in reconfigurable optical add-drop multiplexers, setting the level of dynamic equalization of optical amplifier gain, and providing system alarms and error warnings for lost or non-compliant optical channels.

[0134] It should be noted that the various discussions in this disclosure relate to the frequency of the signal. Those skilled in the art will understand that the concepts discussed in this disclosure also apply to the wavelength of the signal.

[0135] Figure 9 A high-level block diagram of exemplary components of a controller 516 according to various embodiments of this disclosure is depicted. It should be understood that... Figure 9 This description provides only one implementation of controller 516 and does not imply any limitation on the environments in which different embodiments may be implemented. Many modifications can be made to the depicted environment to implement controller 516 without departing from the principles set forth herein. As those skilled in the art will understand, controller 516 can be a server, desktop computer, laptop computer, or any device that can be used to implement this technology.

[0136] As shown in the figure, the controller 516 employs one or more processors 702, one or more computer-readable random access memories (RAM) 704, one or more computer-readable read-only memories (ROM) 706, one or more computer-readable storage media 708, device drivers 714, read / write (R / W) driver interfaces 716, and network interfaces 718, all interconnected via communication structure 720. Communication structure 720 can be implemented by any architecture designed to transfer data and / or control information between processors (such as microprocessors, communication and network processors, etc.), system memory, peripheral devices, and any other hardware components within the system.

[0137] One or more operating systems 710 and one or more application programs 712 are stored on one or more computer-readable storage media 708 for execution by one or more processors 702 via one or more corresponding RAMs 704 (typically including cache memory). In the illustrated embodiment, each computer-readable storage medium 708 may be a disk storage device such as an internal hard disk drive, CD-ROM, DVD, Memory Stick, magnetic tape, magnetic disk, or optical disk; a semiconductor storage device such as RAM, ROM, EPROM, or flash memory; or any other computer-readable tangible storage device capable of storing computer programs and digital information.

[0138] The R / W drive interface 716 reads from and writes to one or more portable computer-readable storage media 726. The application program 712 may be an associated coherent OPM 500 and is stored on one or more portable computer-readable storage media 726, read from and loaded into the corresponding computer-readable storage media 708 via the respective R / W drive interface 716.

[0139] Furthermore, the network interface 718 can be based on a TCP / IP adapter card or a wireless communication adapter (e.g., a 4G wireless communication adapter using OFDMA technology). The application program 712 on the controller 516 can be downloaded to the controller 516 from an external computer or external storage device via a communication network (e.g., the Internet, a local area network, or other wide area networks or wireless networks) and the network interface 718. The application program 712 can be loaded from the network interface 718 onto a computer-readable storage medium 708. The controller 516 can be connected to routers, firewalls, switches, gateway computers, and / or edge servers in the communication network via copper wire, fiber optics, wireless transmission, etc.

[0140] The controller 516 may also include a display screen 722, a keyboard or keypad 724, and a computer mouse or touchpad 728. The device driver 714 may interface with the display screen 722 for imaging, the keyboard or keypad 724, the computer mouse or touchpad 728, and / or with the display screen 722 (which may be a touch-sensitive display) for alphanumeric character input and user selection. The device driver 714, R / W drive interface 716, and network interface 718 may include hardware and software (stored on computer-readable storage media 708 and / or ROM 706).

[0141] Figure 10 A flowchart depicts a process 800 corresponding to various embodiments of the present disclosure and a method for monitoring optical performance implemented on a coherent OPM 500.

[0142] The process 800 begins at step 802, in which the coherent OPM 500 receives an optical channel signal, wherein the optical channel signal is superimposed with a tone-controlled (PT) signal. As previously described, the coherent OPM 500 may include an input port (not shown for simplicity) to receive the optical channel signal whose performance needs to be monitored. The optical channel signal may be superimposed with the PT signal.

[0143] The process 800 proceeds to step 804, in which the coherent OPM 500 causes the LO to operate in coarse scan mode and fine scan mode and generates different LO signals depending on the mode in which the LO operates. As discussed previously, the LO 502 can be used to operate in coarse scan mode and fine scan mode and generate different LO signals. For a given spectral bandwidth, the frequency step size at which the LO 502 generates different LO signals may depend on the mode in which the LO 502 operates.

[0144] The process 800 proceeds to step 806, in which the coherent OPM 500 combines the optical channel signal with at least one LO signal generated by the LO to generate a combined optical signal. As previously described, couplers 506-1 and 506-2 can combine the orthogonally polarized optical channel signal with the orthogonally polarized LO signal to generate a combined optical signal.

[0145] The process 800 proceeds to step 808, in which the coherent OPM 500 detects and converts the combined optical signal. As discussed previously, BPD 508-1 and BPD 506 can convert the outputs of couplers 506-1 and 506-2 (i.e., the combined optical signal) into electrical signals.

[0146] The processing 800 proceeds to step 810, in which the coherent OPM 500 amplifies the electrical signal. As discussed above, TIA 510-1 and TIA 510-2 can amplify the electrical signal and forward the amplified electrical signal to ADC 512-1 and ADC 512-2.

[0147] The processing 800 proceeds to step 812, in which the coherent OPM 500 converts the amplified electrical signal into a digital signal. As mentioned earlier, ADC 512-1 and ADC 512-2 can convert the amplified electrical signal into a digital signal and forward the digital signal to DSP 514.

[0148] The process 800 proceeds to step 814, in which the coherent OPM 500 processes the digital signal and extracts channel-specific information included in the PT signal. As discussed above, the DSP 514 can be used to process the digital signal. Thus, the DSP 514 can extract the PT signal and decode channel-specific information from the PT signal, such as center frequency, modulation format, baud rate, spectral shape, spectral information, source / destination, etc.

[0149] The process 800 proceeds to step 816, in which the coherent OPM 500 calculates the channel power based on channel-specific information. As discussed previously, the DSP 514 can be used to calculate the channel power using channel-specific information.

[0150] Finally, at step 818, the coherent OPM 500 maintains a management table, which includes flags associated with different coarse scan indices (C-indices) and information associated with different channels, where the C-index represents the frequency slot in which the LO signal is generated when the LO operates in coarse scan mode. As described above, the controller 514 can create and maintain management table 600. For each C-index, management table 600 can maintain associated flags and information related to different channels, such as signal flags, PT signal reception flags, channel associations, channel C-indexes, and fine scan flags.

[0151] It should be understood that the operation and functionality of the coherent OPM 500, its components, and associated processes can be implemented using any one or more hardware-based, software-based, and firmware-based components. Such operational alternatives do not in any way limit the scope of this disclosure.

[0152] It should also be understood that although the embodiments presented herein have been described with reference to specific features and structures, it will be apparent that various modifications and combinations can be made without departing from these disclosures. Therefore, the specification and drawings are to be regarded merely as illustrative of the implementations or embodiments of the arguments and their principles as defined in the appended claims, and are intended to cover any and all modifications, variations, combinations, or equivalents falling within the scope of this disclosure.

Claims

1. An optical performance monitor (OPM), comprising: An input port is used to receive optical channel signals, wherein the optical channel signals are superimposed with a tuning (PT) signal; Includes a local oscillator (LO) for the tunable laser, used to operate in coarse scan mode and fine scan mode, and to generate different LO signals depending on the mode in which the LO is operating; At least one optical coupler is used to combine the optical channel signal with at least one LO signal generated by the LO, and generate a combined optical signal; At least one photodetector is used to detect the combined optical signal and convert the detected combined optical signal into an electrical signal; At least one amplifier for amplifying the electrical signal; At least one analog-to-digital converter (ADC) is used to convert an amplified electrical signal into a digital signal; Digital signal processors are used for: The digital signal is processed, and channel-specific information included in the PT signal is extracted. Calculate the channel power based on the channel-specific information; and Controller, used for: Controlling the frequency step size of the LO, and The maintenance management table includes flags associated with different coarse scan indices (C-indices) and information associated with different channels, wherein the C-indices represent the frequency slots in which the LO signals are generated when the LO operates in coarse scan mode.

2. The OPM according to claim 1, characterized in that, The frequency step size of the LO operating in coarse scan mode is larger than that of the LO operating in fine scan mode.

3. The OPM according to claim 1 or 2, characterized in that: When the LO operates in the coarse scan mode, the channel power calculated by the digital signal processor is an approximate channel power, and When the LO operates in the fine scan mode, the channel power calculated by the digital signal processor is the integrated channel power.

4. The OPM according to claim 3, characterized in that, The digital signal processor calculates the power scaling factor based on the approximate channel power and the integrated channel power.

5. The OPM according to claim 4, characterized in that, The digital signal processor corrects the approximate channel power based on the power scaling factor.

6. The OPM according to claim 1 or 2, characterized in that, Compared to the fine scan mode, the LO operates more frequently in the coarse scan mode.

7. The OPM according to claim 1 or 2, characterized in that, The flags in the management table include signal flags and PT signal reception flags.

8. The OPM according to claim 7, characterized in that: If a combined optical signal is detected at the C-index, and the amplitude of the detected signal is higher than a certain threshold, then the signal flag corresponding to the C-index is set to "Y". as well as If no signal is detected at the C-index, or if a combined optical signal is detected at the C-index and the amplitude of the detected signal is below a certain threshold, then the signal flag corresponding to the C-index is set to "N".

9. The OPM according to claim 7, characterized in that: If the channel-specific information is extracted from the digital signal corresponding to the detected optical signal at the C-index, the PT signal reception flag corresponding to the C-index is set to "Y". as well as If the channel-specific information has not yet been extracted from the digital signal corresponding to the detected optical signal at the C-index, the PT signal reception flag corresponding to the C-index is set to "N".

10. The OPM according to claim 7, characterized in that, If the signal flag corresponding to the C-index is set to "Y" and the PT signal reception flag corresponding to the C-index is set to "N", the controller is used to prioritize the extraction of the channel-specific information by instructing the LO to generate an LO signal associated with the C-index.

11. The OPM according to claim 1 or 2, characterized in that: The information associated with different channels in the management table includes entries corresponding to channel association, channel C-index, and fine scan flag. The channel association represents the C-index associated with the channel. The channel C-index represents a C-index selected from the C-indexes associated with the channel, and The fine scan flag indicates whether a fine scan has been performed or not for the channel.

12. The OPM according to claim 11, characterized in that, The C-index associated with the channel is determined by the channel-specific information.

13. The OPM according to claim 11, characterized in that, If the integrated channel power associated with the channel is calculated, the fine scan flag is set to "Y"; otherwise, the fine scan flag is set to "N".

14. The OPM according to claim 11, characterized in that, The frequency step size of the LO operating in coarse scan mode is further reduced based on the selected C-index.

15. The OPM according to claim 1 or 2, characterized in that, If the channel is removed, the controller is also used to update the management table by causing the LO to operate in coarse scan mode.

16. The OPM according to claim 1 or 2, characterized in that, The PT signal includes PT frames, and each PT frame includes all PT information.

17. The OPM according to claim 1 or 2, characterized in that, The PT signal includes sub-PT frames, and each sub-PT frame includes a portion of the PT signal, which includes channel spectrum range information to facilitate coarse and fine scanning.

18. A method for monitoring optical properties, comprising: Receive optical channel signals, wherein the optical channel signals are superimposed with a tuning (PT) signal; The local oscillator (LO), including the tunable laser, is operated in coarse scan mode and fine scan mode, and different LO signals are generated according to the mode in which the LO is operating. The optical channel signal is combined with at least one LO signal generated by the LO to generate a combined optical signal; The combined optical signal is detected and converted into an electrical signal; Amplify the electrical signal; Convert the amplified electrical signal into a digital signal; The digital signal is processed, and channel-specific information included in the PT signal is extracted; Calculate the channel power based on the channel-specific information; and The maintenance management table includes flags associated with different coarse scan indices (C-indices) and information associated with different channels, wherein the C-indices represent the frequency slots in which the LO signals are generated when the LO operates in coarse scan mode.

19. The method according to claim 18, characterized in that, The frequency step size of the LO operating in coarse scan mode is larger than that of the LO operating in fine scan mode.

20. The method according to claim 18 or 19, characterized in that: The channel power calculated when the LO operates in the coarse scan mode is an approximate channel power, and The channel power calculated when the LO operates in the fine scan mode is the integrated channel power.

21. The method of claim 20, further comprising calculating a power scaling factor based on the approximate channel power and the integrated channel power.

22. The method according to claim 21, characterized in that, The approximate channel power is corrected based on the power scaling factor.

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