Method and apparatus for hardware-configured networking

Abstract

The present disclosure relates to methods and devices for hardware-configured networks. An optical transceiver includes: a tunable transmitter having an electrical input and an optical output, the tunable transmitter configured to generate one of the following: 1) an optical transmit signal at the optical output for performing a slow scan of wavelength channels with a first dwell time per channel; and 2) an optical transmit signal at the optical output for performing a fast scan of wavelength channels with a second dwell time per channel, the first dwell time being greater than the second dwell time; a receiver having an electrical output and an optical input for receiving an optical receive signal; and a processor having an input connected to the electrical output of the receiver and an output connected to the electrical input of the tunable transmitter, the processor determining a characteristic of the optical receive signal and instructing the tunable transmitter to generate an optical transmit signal having a fast scan of wavelength channels with the second dwell time per channel in response to the determined characteristic.

Description

[0001] This application is a divisional application of the invention patent application with the application date of October 14, 2018, application number 201880074041.1, and name “Method and device for hardware configured network”. Background Art

[0002] The increasing demand for high-capacity data transmission through optical fibers and the increasing number of optical network elements that are flexibly and dynamically networked together pose a great challenge to the fiber optic telecommunications industry. For example, higher capacity demands require that more transceiver wavelengths be more closely spaced together in the spectral domain to provide higher capacity on a single optical fiber or connection. These high-capacity, high-channel-count systems require more real-time performance data monitoring to control transceivers. In addition, the larger number of transceivers required for these high-capacity, high-channel-count systems requires a higher degree of automation of transceiver configuration to improve reliability and reduce human operation. In addition, the network is configured to include an increased number of various optical components (including transceivers, amplifiers, wavelength filters, wavelength multiplexers, wavelength demultiplexers, cross-connects, optical switches, passive splitters, and combiners) that require automation and control solutions that can operate on various optical component types.

[0003] It is desirable for high-capacity, high-channel-count systems to have automated configuration that allows network elements to self-provision and self-monitor to reduce the burden on network operators during network turn-up and during ongoing operation. Such automation allows larger-scale optical networks to be constructed and operated at lower costs.

[0004] High-capacity, high-channel-count optical communication systems are also desired to have dynamic and reconfigurable optical networks that provide increased network flexibility and bandwidth utilization. These optical communication systems often require real-time configuration in response to changing conditions and data communication demands. In addition, support for dynamic traffic routing requires advanced wavelength and channel monitoring to tune transceiver and wavelength selective switch (WSS) wavelengths.

[0005] Additionally, scaling optical communication systems to achieve high capacity and high channel counts requires providing enhanced deployment capabilities within the same or smaller footprints than currently deployed optical communications. Therefore, it is desirable to have deployment methods and apparatus that reuse and / or rely heavily on existing network components. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The present teachings according to preferred exemplary embodiments and their additional advantages are described in more detail in the detailed description below in conjunction with the accompanying drawings. Those skilled in the art will appreciate that the drawings described below are for illustrative purposes only. The drawings are not necessarily to scale, but rather the emphasis is generally on illustrating the principles of the teachings. In the drawings, like reference numerals generally denote like features and structural elements throughout the various figures. The drawings are not intended to limit the scope of applicant's teachings in any way.

[0007] Figure 1A A block diagram representing an embodiment of optical components of a hardware configuration according to the present teachings.

[0008] Figure 1B Block diagram of an embodiment of an optical component representing a hardware configuration of the present teachings, wherein an optical carrier signal is generated internally within the optical component.

[0009] Figure 1C Block diagram of an embodiment of an optical component representing a hardware configuration of the present teachings, wherein the optical carrier signal originates external to the optical component.

[0010] Figure 1D A block diagram illustrating one embodiment of an optical component including a hardware configuration of an optical transceiver.

[0011] Figure 1E Indicates combination Figure 1D An oscilloscope trace depicting the measured output of an optical transceiver on the transmit fiber.

[0012] Figure 2A A block diagram illustrating an embodiment of an optical component of a hardware configuration of the present teachings including an optical transceiver having a tunable transmitter.

[0013] Figure 2B Spectra representing the measured output of a tunable transceiver on a transmitting fiber according to the present teachings are shown.

[0014] Figure 2C A long time scale oscilloscope trace showing a low frequency modulation measured on a transmitting optical fiber at the output of a tunable transceiver in accordance with the present teachings.

[0015] Figure 3A An embodiment of a network element comprising a wavelength selective switch according to a hardware configuration of the present teachings is shown.

[0016] Figure 3B An oscilloscope trace showing the measured output of a wavelength selective switch showing a low frequency control signal in accordance with the present teachings.

[0017] Figure 4 Block diagram showing one embodiment of optical components including a hardware configuration of an optical amplifier according to the present teachings.

[0018] Figure 5 An oscilloscope trace showing a low frequency control signal according to the present teachings including a collision avoidance protocol based on a modification of the well-known Ethernet protocol.

[0019] Figure 6 An embodiment of a network of hardware configurations of the present teachings is represented in a point-to-point transceiver topology (sometimes referred to in the art as an optical link).

[0020] Figure 7 An embodiment of a network of hardware configurations of the present teachings is shown including a plurality of tunable transceivers connected to wavelength selective switches or optically programmable filtering elements.

[0021] Figure 8 An embodiment of a network of hardware configurations of the present teachings is shown including a wavelength division multiplexing network having wavelength selective switch optical elements.

[0022] Figure 9 express Figure 8 A hardware configuration of a network where the wiring is incorrectly installed in location B.

[0023] Figure 10 express Figure 8 A network of hardware configurations where the installer made an error when wiring a component at location A.

[0024] Figure 11 An embodiment of a low-cost combiner-splitter comprising elements of a hardware configuration according to the present teachings is shown.

[0025] Figure 12A A block diagram illustrating an embodiment of a hardware configurable link of a tunable transceiver including a hardware configuration of the present teachings.

[0026] Figure 12B Indicates that it can be combined with Figure 12A A block diagram of an embodiment of a transceiver according to the present teachings is described for use with a hardware configurable link.

[0027] Figure 13 Graphs showing optical power as a function of time for an embodiment of a set of transmitter states according to the present teachings are shown.

[0028] Figure 14 A graph showing optical power as a function of time is shown for a set of transmitter and receiver states present during an embodiment of a method of connecting a protocol of the present teachings.

[0029] Figure 15 A flow chart representing an embodiment of a protocol for establishing a link using transceiver elements of the hardware configuration of the present teachings.

[0030] Figure 16Graph representing measured optical signals for an embodiment of a method for configuring an optical link using a transceiver configured with hardware according to the present teachings.

[0031] Figure 17A A top view of an embodiment of a transceiver showing a hardware configuration according to the present teachings.

[0032] Figure 17B Represents Figure 17A Bottom view of the transceiver incorporating the described hardware configuration.

[0033] Figure 17C A top view of another embodiment of a transceiver showing a hardware configuration according to the present teachings.

[0034] Figure 18 Schematic diagram showing an embodiment of optoelectronic components in a transceiver of a hardware configuration according to the present teachings.

[0035] Figure 19A Schematic diagram showing an embodiment of a WDM transport system including a transceiver of the hardware configuration of the present teachings.

[0036] Figure 19B Indicates the state of the embodiment of the setting protocol of the hardware configuration of the present teaching Figure 19A Schematic diagram of the WDM transmission system.

[0037] Figure 19C In another embodiment of the hardware configuration setting protocol of the present teachings Figure 19A Schematic diagram of the WDM transmission system.

[0038] Figure 19D In another embodiment of the hardware configuration setting protocol of the present teachings Figure 19A Schematic diagram of the WDM transmission system.

[0039] Figure 19E In another embodiment of the hardware configuration setting protocol of the present teachings Figure 19A Schematic diagram of the WDM transmission system.

[0040] Figure 20 An embodiment of a remote PHY subsystem with gain of the present teachings is shown.

[0041] Figure 21 Schematic diagram showing an embodiment of a WDM transmission system having gain of a transceiver utilizing a hardware configuration according to the present teachings.

[0042] Figure 22A An embodiment of a remote PHY system of a network element using a hardware configuration of the present teachings configured for telecommunications applications is shown.

[0043] Figure 22B An embodiment of a remote PHY system is shown that utilizes a hardware-configured network element of the present teachings configured for data communications applications.

[0044] Figure 23A An embodiment of a front panel of a remote PHY system of a network element using the hardware configuration of the present teachings is shown.

[0045] Figure 23B An embodiment of a rear panel of a remote PHY system of a network element using the hardware configuration of the present teachings is shown.

[0046] Figure 24 A schematic diagram showing the functional blocks and layout of an embodiment of a Remote PHY system supporting two Remote PHYs for a network element using the hardware configuration of the present teachings.

[0047] Figure 25 Schematic diagram showing an embodiment of a WDM transport link utilizing two unidirectional optical fibers to connect tunable transceivers in a hardware configuration using fixed AWG filters in accordance with the present teachings.

[0048] Figure 26A express Figure 25 A state diagram of an embodiment of a method for automatic channel discovery of an optical link of a hardware configuration.

[0049] Figure 26B express Figure 25 A process flow chart of an embodiment of a method for automatic channel discovery of an optical link in a hardware configuration.

[0050] Figure 27A Indicates that Figure 25 An embodiment of a method of link connection associated with a hardware configuration of an optical link includes a graph of optical power as a function of time for a set of transmitter and receiver states and an associated state timing diagram.

[0051] Figure 27B An experimental setup for measuring optical power as a function of time for an embodiment of a method of link connection associated with an optical link of a hardware configuration of the present teachings is shown.

[0052] Figure 27C Indicates that Figure 27B An embodiment of a method of hardware configuring a connection protocol associated with an optical link displays an oscilloscope trace of optical power as a function of time.

[0053] Figure 28A Schematic diagram showing an embodiment of a WDM transport link utilizing two unidirectional optical fibers to connect tunable coherent transceivers configured in hardware using a filter-based combiner / splitter according to the present teachings.

[0054] Figure 28B express Figure 28A A state diagram of an embodiment of a method for automatic channel discovery of an optical link of a hardware configuration.

[0055] Figure 28C express Figure 28A A process flow chart of an embodiment of a method for automatic channel discovery of an optical link in a hardware configuration.

[0056] Figure 28D Indicates that Figure 28A A graph showing optical power as a function of time for a set of transmitter and receiver states present during an embodiment of a method for automatic channel discovery of an optical link in a hardware configuration.

[0057] Figure 29 Schematic diagram showing an embodiment of a WDM transport link utilizing two unidirectional optical fibers to connect tunable coherent transceivers configured in hardware using a non-filter based combiner / splitter according to the present teachings.

[0058] Figure 30A 1 shows a spectrum produced by a transceiver in a startup state according to an embodiment of a method using a connection protocol of the present teachings.

[0059] Figure 30B 1 shows a spectrum generated by a transceiver in an established link operation state according to an embodiment of a method using a connection protocol of the present teachings.

[0060] Figure 30C A time series of optical spectra of a transceiver in a tuned state without RF modulation is shown according to an embodiment of a method using a connection protocol of the present teachings.

[0061] Figure 30D Spectral time series showing a link in a tuned state with RF modulation on channel 1 according to an embodiment of a method using a connection protocol of the present teachings.

[0062] Figure 31 Schematic diagram showing an embodiment of a bidirectional WDM transport link utilizing a coherent hardware configured transceiver with an AWG splitter according to the present teachings.

[0063] Figure 32 Schematic diagram showing an embodiment of a bidirectional WDM transport link utilizing coherent hardware-configured transceivers with filterless passive splitters in accordance with the present teachings.

[0064] Figure 33AA time series of optical spectra of a transceiver in a tuned state without RF modulation is shown according to an embodiment of a method using a connection protocol of the present teachings.

[0065] Figure 33B Spectral time series showing how a transceiver without RF modulation can be tuned with wait times between sequences to avoid collisions according to an embodiment of a method of using a connection protocol of the present teachings.

[0066] Figure 33C Spectra of a transceiver with RF modulation after a successful connection completion according to an embodiment of a method using a connection protocol of the present teachings are shown.

[0067] Figure 34A A time series of spectra relating to the status of the search and connection steps is shown according to an embodiment of a method using a connection protocol of the present teachings.

[0068] Figure 34B Spectral time series relating to the state of a transceiver and associated LO laser are shown according to an embodiment of a method of using a connection protocol of the present teachings.

[0069] Figure 35 1. A set of time series according to an embodiment of a method using a connection protocol of the present teachings is shown for an unfiltered optical link showing search and detection.

[0070] Figure 36A Spectral timing diagram illustrating an embodiment of a link establishment method for a coherent link with a non-filtering passive splitter / combiner according to the present teachings.

[0071] Figure 36B Indicates that Figure 36A FIG. 1 is a combined spectrum timing diagram of an embodiment of a link establishment method for a coherent link using a non-filtering passive splitter / combiner. DETAILED DESCRIPTION

[0072] The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described in this application in any way.

[0073] CROSS-REFERENCE TO RELATED APPLICATIONS

[0074] This application claims priority to U.S. Provisional Patent Application Serial No. 62 / 573,142, entitled “Method and Apparatus for Hardware-Configured Network,” filed on October 16, 2017. The entire contents of U.S. Provisional Patent Application Serial No. 62 / 573,142 are incorporated herein by reference.

[0075] Reference in the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the teachings. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

[0076] Should be understood that the various steps of the method of this teaching can be performed in any order and / or simultaneously, as long as this teaching is still operable.In addition, should be understood that the apparatus and method of this teaching can include any number of described embodiments or all of the described embodiments, as long as this teaching is still operable.

[0077] This teaching will now be described in more detail with reference to the exemplary embodiments of this teaching as shown in the accompanying drawings. Although this teaching is described in conjunction with various embodiments and examples, this teaching should not be limited to such embodiments. On the contrary, as will be appreciated by those skilled in the art, this teaching includes various alternatives, variations and equivalents. Those of ordinary skill in the art who access this teaching here will appreciate that other implementations, variations and embodiments within the scope of this disclosure as described herein and other areas of use.

[0078] The terms "element" or "network element" are used herein to describe the various devices and optical subsystems used to establish and operate an optical network. Some examples of these devices and optical subsystems are transceivers, switches, wavelength selective switches, programmable filters, amplifiers, add-drop multiplexers, and cross-connects. As used herein, the term "component" describes the optical, mechanical, and electronic components that make up these subsystems. The term "network" describes multiple network elements that are connected to form a group or system of elements that exchange information and operate in a collaborative manner.

[0079] When used in conjunction with a network in this disclosure, the term "configuration" is intended to include various network management, control, and operation functions. For example, the term "configuration" includes various tasks such as element inspection, element diagnosis, element performance monitoring, and control of element operating parameters. Some terms in the art that should be considered part of the definition of "configuration" include network management, network operations, FCAPS (fault management, configuration, accounting, performance, security), and network monitoring and alerting. Network management includes various tasks such as configuring, discovering, identifying, and inspecting network elements, discovering and reacting to faults or misconfigurations of network elements, and monitoring the performance of network elements. In addition, the term "configuration" can apply to a single element, or it can apply to a group of elements used or intended to be used as a connected system or network. In particular, the term "configuring a network" includes various tasks such as network discovery, passive monitoring, and active control of network operations.

[0080] Prior art optical network components are primarily configured via optical client interfaces. Little or no management information is exchanged directly between components (such as transceivers, wavelength selective switches, amplifiers, and other components in the optical network). Configuration information is typically sent over a single channel, which limits the amount of management information and the number of network components that can be configured. The single management or supervisory channel also limits the amount of information available to external network management systems, particularly during startup operations.

[0081] Additionally, in prior art optical network configuration systems, a large amount of diagnostic information is sent from network elements to one or more external network management systems or users for processing. The diagnostic information is processed in the external network management system, and instructions are then sent back to the elements to effect network configuration changes. This remote and / or hands-on configuration architecture of known systems limits the scale of networks that can be configured. This limitation is particularly true as the amount of information from network elements that needs to be processed increases in order to improve element monitoring and / or provide dynamic element operation. For example, support for dynamic traffic routing requires optical elements that provide a large amount of real-time data for optical path calculations, including embedded amplifier performance and dynamic path spectrum conditions.

[0082] Therefore, it is highly desirable to have methods and apparatus for configuring elements in an optical network that are automated, tunable across multiple channels, and that operate on the various optical elements comprising the network. The present teachings relate, at least in part, to embodiments of methods and apparatus for transmitting and processing control and management information for a hardware-configured network (HCN). As used herein, the term "hardware-configured network" is a networked system of optical and electrical switching and transmission elements and components that automatically configure, control, and manage their operation with little or no user input.

[0083] One possible characteristic of a hardware-configured network is that it automatically connects and provisions channels and wavelengths without centralized commands or user intervention. Another possible characteristic of a hardware-configured network is that it detects and corrects configuration errors without centralized commands or user intervention. Another possible characteristic of a typical hardware-configured network is that it reconfigures optical components without centralized commands or user intervention. Examples of configurations performed by a hardware-configured network include component activation, tuning of tunable components, programming of programmable optical filter characteristics (such as bandwidth, filter shape, dispersion, and other configurable parameters), setting the attenuation level of a wavelength selective switch (WSS), setting the gain and gain spectrum on an erbium-doped fiber amplifier (EDFA), configuring ports and wavelengths per port for optical switches and wavelength add / drop multiplexers and cross-connects, and optical link establishment. Although aspects of the hardware-configured network of the present teachings are described in conjunction with self-configuration of network elements, those skilled in the art will appreciate that user and / or centralized commands or external management systems with access to configuration control and information for the hardware-configured network may also be used in conjunction with self-configuration of network elements.

[0084] Figure 1A A block diagram illustrating an embodiment of an optical element configured in accordance with the present teachings. A network configured in accordance with the present teachings uses low-frequency modulation (rather than using a dedicated supervisory optical channel) to transmit control information over the network. That is, the low-frequency modulated optical carrier used to transmit and receive control information is a portion of the optical signal propagating through the network. These optical signals used as optical carriers in various embodiments of the network configured in accordance with the present teachings can include client data traffic, spurious signals, CW light, and amplified spontaneous emission. As used herein, the term "optical carrier" is defined as any light to which modulation (which can be low-frequency modulation) is applied. This definition is broader than other uses of the term in the art. For example, in some applications of optical communications, the term "optical carrier" is used to describe light of a specific wavelength used to transmit data, often a wavelength based on the ITU grid from a laser transmitter. In various embodiments, the optical carrier can be generated in the optical element itself, or it can be an optical carrier received from the network.

[0085] Hardware-configurable optical component 100 includes an electronic control port 102 for transmitting and receiving electrical control information. It also includes an electronic control port 103 for transmitting and receiving client data traffic. Hardware-configurable optical component 100 also includes an output port coupled to a transmit optical fiber 104 for transmitting optical signals to an optical network, and an input port coupled to a receive optical fiber 106 for receiving optical signals from the optical network. A demodulator 108 decodes received control information from receive optical fiber 106 and transmits the decoded control information to a control processor 110, which processes the information and then configures the optical component based on the control information.

[0086] Optical modulator 112 modulates the optical carrier with the transmit control information so that the transmit control information can be transmitted into the optical network. In one method of operation, optical modulator 112 modulates the optical carrier with a low-frequency modulation representing the transmit control information. The transmit optical control signal is then transmitted to the network using transmit optical fiber 104. In some methods of operation, the transmit optical control signal is directly applied to the client data signal used as the optical carrier, and this combined modulated optical signal is then transmitted over transmit optical fiber 104.

[0087] Figure 1BA block diagram illustrates an embodiment of an optical component 120 in a hardware configuration according to the present teachings, wherein the optical carrier signal is generated internally within the optical component. Specifically, the optical carrier signal is generated by an optical signal generator 122 located within the optical component. In some embodiments, the optical signal generator 122 is part of a client transmitter within the optical transceiver component. In some embodiments, the transceiver operates using a coherent signaling format. In some embodiments, the optical transceiver is a tunable coherent transceiver, and the optical signal generator is a tunable laser that generates a local oscillator signal. In some embodiments, the optical signal generator 122 includes an optical amplifier, and the optical carrier is amplified spontaneous emission. A modulator 124 is used to modulate the optical carrier with control information. In some operating methods, the control information is generated by a local processor 126. In other operating methods, the control information is generated by a remote source having an output electrically connected to an electronic control port 128. In some embodiments, the optical amplifier gain generated by the optical amplifier that is part of the optical signal generator 122 is controlled by a pump laser. Low-frequency modulation is implemented as a gain variation over time. Therefore, in some embodiments, modulator 124 is a gain controller. In embodiments including an optical amplifier modulated to add control information, if no optical carrier signal is present, the amplified spontaneous emission from the amplifier carries the control information. If, on the other hand, one or more carriers are present, the gain modulation imparts information to each of the one or more carriers. These various carriers can then, for example, follow different paths in the optical network, as they may occupy different wavelength channels that are routed differently. Port 136 is also provided for transmitting and receiving client data traffic, connected to modulator 124 and demodulator 134. Splitter 130 is used to separate a portion of the input optical signal that includes a received control signal from optical network 132. Demodulator 134 decodes the received control information and then transmits it to control processor 126, which configures hardware-configured elements 120 based on the provided control information.

[0088] Figure 1CA block diagram illustrates an embodiment of a hardware-configured optical component 140 according to the present teachings, wherein an optical carrier signal originates externally from the optical component. The optical carrier originates from an optical network and arrives at an input fiber 142. A portion of the optical signal from input fiber 142 is split by a splitter 144 and sent to a demodulator 148. Demodulator 148 decodes receive control information and then sends the receive control information to a control processor 149, which configures the hardware-configured component 140 based on the provided control information. A portion of the optical signal is split by splitter 144 and sent to an optical modulator 146, which applies transmit control information to the optical carrier in the form of a low-frequency modulation. The transmit optical control signal then exits the optical component on a transmit fiber 147. A port 150 for client data traffic is also provided and is connected to demodulator 148 and modulator 146. In some embodiments, a wavelength selective switch with a photodiode is used as demodulator 148. In some embodiments, a VOA with a wavelength selective switch is used as modulator 146.

[0089] In some embodiments, the optical carrier comprises a client data signal generated by an optical transceiver element located upstream of the hardware configuration's optical element 140. In some embodiments, the client data signal is generated using a coherent signaling format. In other embodiments, the optical carrier comprises amplified spontaneous emission from an upstream optical amplifier. Figure 1D A block diagram illustrates one embodiment of an optical component including a hardware configuration of an optical transceiver 150. Optical transceiver 150 includes an electrical control port 152 for sending and receiving electronic command and control information. Electrical port 158 ​​provides and receives client data traffic. In some embodiments, electrical control port 152 is an industry-standard I2C interface. In other embodiments, electrical control port 152 utilizes a multi-master, multi-slave serial protocol for embedded system control. Optical transceiver 150 also includes an output optically coupled to a transmit fiber 154 and an input optically coupled to a receive fiber 156, which transmits optical signals to optical transceiver 150. The optical signals in both transmit fiber 154 and receive fiber 156 can include either or both client data traffic and low-frequency control signals. Client data traffic can include network traffic transmitted over the network. The low-frequency control signals can include various types of information used to configure the network component.

[0090] Figure 1E Indicates combination Figure 1D An oscilloscope trace of the measured output 160 of the optical transceiver 150 on the transmit optical fiber 154 is depicted. Figure 1D and 1EIn this embodiment, optical transceiver 150 generates client data traffic 162 at a data rate of 10 Gb / s. Client data traffic 162 appears as high and low data levels as a function of time over a relatively long time scale. Modulated control signal 164 uses a string of "1s" and "0s" at a low frequency that is directly applied to the optical communication signal including client data traffic 162.

[0091] Therefore, one aspect of the present teachings is to encode the control signal 164 using a string of ones and zeros at a low frequency that is directly imposed on the optical communication signal from the transceiver 100. Figure 1D 、 1E In the embodiment shown in FIG, the control signal 164 is applied directly to the client data traffic 162 generated by the transceiver 150. In various embodiments, the low frequency "1" and "0" can be decoded at corresponding receiving optical elements (not shown) optically coupled to the transmitting optical fiber 154. The low frequency modulation can be amplitude modulation, such as Figure 1E In various other embodiments, the low frequency modulation can be any modulation format, such as phase modulation or frequency modulation.

[0092] It is important to note that client data traffic 162 is unaffected by the low-frequency modulation. One advantage of encoding the control signal using a low-frequency string of ones and zeros 164 to provide the control signal 164 applied directly to the optical signal from transceiver 150 is that the frequencies used for the low-frequency modulation are typically incapable of passing through the electrical filters in the receiver that decode the high-data-rate client data traffic 162. Depending on the details of the modulation, scrambling, and encoding of the optical signal, baseline wander can set the low-frequency cutoff of these high-pass electrical filters to as low as 100 kHz. Therefore, the frequency of the low-frequency control signal is selected to be below the lowest frequency of the high-pass filtering used in the transceiver, and thus, the low-frequency control signal will not affect the integrity of the client data traffic 162. Furthermore, encoding and decoding based on low-frequency modulation can be accomplished using relatively low-cost, low-bandwidth optical and electronic equipment that is well known and widely available in the art. Some embodiments of networks configured according to the present teachings utilize optical and electrical components already present in currently deployed transceivers 150.

[0093] Figure 2AA block diagram 200 illustrates one embodiment of an optical component including a hardware configuration of an optical transceiver with a tunable transmitter 202. The optical transceiver may also include a detector and a receiver. In some embodiments, the detector and receiver may be an LO (Lower Oscillator) detector and receiver that can process signals from a link. In some embodiments, the tunable transmitter 202 also includes a receiver with a detector, which may also include a local oscillator (LO) detector for coherent detection of incoming signals. Some embodiments use two LO lasers, one for transmission and one for reception, while some embodiments use a single LO laser for both transmission and reception. The tunable transceiver 202 includes an electrical control port having an electrical input 204 for transmitting and receiving command and control information. Additionally, a port 208 is provided for inputting client data traffic. In some embodiments, the input port 208 for inputting client data traffic may be the same input port as the electrical input 204 for transmitting and receiving command and control information. The input port 208 may be an electrical port. In some embodiments, the tunable transceiver 202 uses a coherent modulation format to generate optical signals and uses a coherent receiver to receive signals. In some embodiments, the electrical control port 204 is an industry standard I2C interface. In other embodiments, the electrical control port 204 uses a multi-master multi-slave serial protocol for embedded system control. The tunable transceiver 202 includes an output that is optically coupled to a transmit and receive optical fiber 206. The transmit and receive optical fibers 206 provide optical signals to and receive optical signals from the optical link for communication of data signals and control signals of the present teachings. The signals received from the receive optical fiber 206 are detected by a detector and receiver, which may be an LO detector and receiver that can process the signals from the link.

[0094] Figure 2B Spectrum 208 representing the measured output of a tunable transceiver on a transmit fiber 206 according to the present teachings is shown. Spectrum 208 indicates that a tunable laser in tunable transceiver 202 generates a modulated signal on a particular wavelength channel 210. In one particular embodiment, the tunable transceiver 202 wavelength or channel can be set and adjusted over a wavelength range from 1528 nm to 1567 nm.

[0095] Reference Figure 2A and 2BIn this embodiment, optical transceiver 200 is generating customer data traffic 224 at a 10 Gb / s data rate. Using a relatively long time scale of an oscilloscope trace 220 measuring the modulated signal on a specific wavelength channel 210, customer data traffic 224 is shown as high and low data levels as a function of time. Control and management information used to configure the network is encoded as low-frequency strings of "ones" and "zeros" 222 applied directly to customer data traffic 224. In some operating methods according to the present teachings, the typical output power of tunable transceiver 202 is in the 0-3 dBm range, corresponding to approximately 1-2 mW. Furthermore, in some operating methods, the low-frequency coded modulation format is a low-frequency power variation of the tunable laser channel, thereby operating at the wavelength of the laser channel setpoint. Furthermore, in some operating methods, the modulation depth of the low-frequency modulation is between approximately 0.5% and 10%. In some embodiments, the low-frequency modulation is 5% or less. In various embodiments, customer data traffic 224 uses various known modulation formats. For example, client data traffic 224 may utilize coherent modulation.

[0096] A feature of the present teachings is that low frequency modulation can appear as high-dead low frequency modulation. For example, Figure 2A The transceiver can be turned on and off at a low frequency. In this case, the control signal "0" will be when the transceiver is turned off, and the low frequency "1" will be when the transceiver is turned on. Figure 2C A long time-scale oscilloscope trace 240 shows low-frequency modulation measured at the output of a tunable transceiver on a transmit optical fiber in accordance with the present teachings. Transceiver client data traffic 242 is generated at a 10 Gb / s data rate. Control and management information used to configure the network is encoded as a low-frequency string of "ones" and "zeros" 244 applied directly to the client data traffic 242 and shown as high and low data levels as a function of time using the relatively long time scale of oscilloscope trace 240. In this embodiment, the decay of the low-frequency modulation is very high; however, the frequency of the low-frequency control signal is selected to be below the lowest frequency of the high-pass filtering used in the transceiver, so the low-frequency control signal will not affect the integrity of the client data traffic 242.

[0097] Therefore, a feature of a network configured with hardware according to the present teachings is that control information is encoded on a tunable transmitter signal, and therefore the wavelength carrying the encoded control information is tunable based on the tuning configuration of the tunable transmitter. Thus, by tuning the wavelength of the signal carrying the encoded information, the destination of the encoded control information can be changed based on the specific wavelength paths configured in the optical network. For example, the configuration of wavelength switches, filters, and amplifiers in the optical network establishes wavelength paths from source to destination in the optical network. The wavelength paths from various sources to various destinations can also be changed based on the reconfiguration of network components. The source wavelength can be tuned to adopt a desired wavelength path to a specific destination or set of destinations, and thus, a low-frequency control signal applied to the optical signal at that source wavelength will deliver the encoded control information to that specific destination or set of destinations. Thus, by simply tuning the laser wavelength of the tunable transceiver, the destination of the low-frequency control signal can be changed. This ability to select the wavelength carrying the low-frequency modulated control signal by selecting a specific wavelength path allows encoded control information from one network element to reach any of a variety of different elements in the network.

[0098] Another feature of a network configured with hardware according to the present teachings is that the low frequency encoding of control signals on a particular wavelength does not affect other wavelengths propagating in the optical fiber or throughout the optical network.

[0099] Figure 3A 1 shows an embodiment of an optical element 300 including a wavelength selective switch 302 configured in accordance with the present teachings. In some embodiments according to the present teachings, the wavelength selective switch 302 is a standard, commercially available wavelength selective switch 302 without special modifications. Wavelength selective switches exist in a wide range of port configurations and channel plans and are currently used in prior art optical networks. Wavelength selective switches, such as those manufactured by Finisar Corporation, provide a highly programmable and flexible switching platform that switches traffic from one optical link to another over multiple wavelengths in the same network. However, wavelength selective switches according to the present teachings can be configured with additional features according to the present teachings. In one embodiment of the present teachings, the wavelength selective switch 302 includes one or more low-frequency photodiodes for directly detecting encoded control data.

[0100] Additionally, wavelength selective switches used in a network configured according to the hardware of the present teachings are bidirectional and capable of operating equally in both directions. Thus, one aspect of the present teachings is that the wavelength selective switch 302 is also capable of receiving and decoding control signals from other optical components in the network, as well as transmitting and encoding control signals intended for other optical components in the network.

[0101] The hardware-configured optical component 300 includes a wavelength selective switch 302 having at least one optical input optically connected to a receiving optical fiber 304 and a plurality of optical outputs optically connected to a plurality of transmitting optical fibers 306, 306', 306". The wavelength selective switch 302 also has an electrical control port 308. In some operating methods according to the present teachings, the receiving optical fiber 304 propagates optical signals at one or more wavelengths. Return to reference Figure 2A 、 2B , the optical signal may include client data traffic originating from the tunable optical transceiver 202 .

[0102] Figure 3A 3 shows client data traffic 310 received on optical fiber 304. One function typically performed by wavelength selective switch 302 is to vary the attenuation of a received optical signal in response to an electronic control signal and to generate an amplitude modulated signal by varying the attenuation. Consequently, low-frequency modulation applied to an optical signal received at the optical input of wavelength selective switch 302 can be independently applied to optical signals at any or all wavelengths or channels passing through wavelength selective switch 302.

[0103] Figure 3A Also shown is client data traffic 310 with a low-frequency control signal 312 in the form of a string of ones and zeros encoded by an electronic control signal. It is important to note that the integrity of client data traffic 310 is not affected by the low-frequency control signal. Using the electronic control signal that selectively controls the attenuation of specific wavelength channels of the wavelength selective switch 302, the low-frequency control signal is selectively applied to the desired wavelength channel routed to any of the plurality of transmit fibers 306, 306', 306".

[0104] The low frequency control signal in the form of a string of "1"s and "0"s 312 generated by the wavelength selective switch 302 can be filtered to eliminate high frequency signals from the client data traffic, such as Figure 3B This is shown in the oscilloscope trace 350 shown in FIG. Figure 3B An oscilloscope trace 350 is shown of the measured output of a wavelength selective switch 302 displaying a low-frequency control signal in accordance with the present teachings. The measured output is measured at a receive optical fiber 306, where the client data traffic is filtered in accordance with the present teachings. The result is a first signal level of "1" obtained by low attenuation of the wavelength selective switch 302 and a second, lower signal level of "0" obtained by higher attenuation of the wavelength selective switch 302. The data rate of the filtered control signal can be relatively low. For example, the data rate of the low-frequency control signal can be approximately 5 bits / s, which is lower than the client traffic rate.

[0105] Figure 4A block diagram illustrating one embodiment of an optical amplifier 400 configured in hardware according to the present teachings. In the illustrated embodiment, the optical amplifier 400 configured in hardware is an erbium-doped fiber amplifier (EDFA), which is a common optical amplifier used in modern optical communication systems. Those skilled in the art will appreciate that many other types of optical amplifiers can be used, including Raman and / or Raman / EDFA combinations. The optical amplifier 400 includes an electrical control port 402 configured to send and receive electrical command and control information. In accordance with the present teachings, the optical amplifier 400 also includes an optical input port coupled to a receive fiber 404 that provides an optical signal to be amplified, and an optical output port coupled to a transmit fiber 406 that transmits the amplified optical signal, which may also include a low-frequency control signal.

[0106] Figure 4 Also shown is an oscilloscope trace of input client data traffic 408 provided by receive optical fiber 404 to be amplified by optical amplifier 400. In this embodiment, client data traffic 408 is modulated at, for example, a 10 Gb / s data rate. Optical amplifier 400 varies the attenuation of the received optical signal and generates a low-frequency amplitude-modulated control signal 410.

[0107] exist Figure 4 In the embodiment shown in FIG, configuration information is encoded on a low frequency modulated control signal using an electronic control signal provided by control port 402. Using low frequency modulation applied to client data traffic 408, the configuration information data in the low frequency amplitude modulated control signal 410 is encoded as a string of "1s" and "0s", such as Figure 4 As shown in , the integrity of the client data traffic 408 is not affected by the low-frequency amplitude modulation control signal because the amplitude modulation depth of the low-frequency modulation is small relative to the modulation depth of the client data traffic. Furthermore, the integrity of the client data traffic 408 is not affected by the low-frequency amplitude modulation control signal because the frequency of the low-frequency modulation is too low to pass through the receive filter for the client data traffic.

[0108] As described herein, one feature of a network configured with hardware according to the present teachings is that the integrity of client data traffic 408 is unaffected by the small amount of low-frequency modulation applied by optical amplifier 400. In some embodiments, the amplitude modulation applied by optical amplifier 400 provides low-frequency modulation across the entire spectral bandwidth of optical amplifier 400. In other words, all channels amplified by the optical amplifier experience substantially the same low-frequency modulation. In these embodiments, all channels passing through optical amplifier 400 receive the same encoded information from the electronic control signal. However, in other embodiments of the present teachings, optical amplifier 400 includes a gain control capable of controlling the gain of a specific channel or band of channels passing through optical amplifier 400. In these embodiments, the control signal is encoded on one or more selected channels, wavelengths, or frequency bands passing through optical amplifier 400. In some embodiments, the modulation is encoded by modulating the power of a pump laser that controls the gain of amplifier 400.

[0109] A feature of the present teachings is that the low frequency control signal can be applied to various types of existing optical signals. Figures 1D-1E In the embodiments shown in FIG2 and FIG3 , the existing optical signal includes client data traffic originating from a transceiver component. In some embodiments, the existing optical signal does not include real-time data traffic. For example, the existing optical signal can include a pseudo communication data signal. In other embodiments, the existing optical signal includes a CW output of an optical transceiver or amplified spontaneous emission from an optical amplifier.

[0110] Furthermore, in some embodiments, the existing optical signal originates from the same optical component that applies the electronic control information to the existing optical signal. In other embodiments, the existing optical signal originates from another optical component located upstream of the optical component that applies the electronic control information to the existing optical signal. In some embodiments, electronic control information from one or more separate components connected in the network is applied to the same existing optical signal. In some embodiments, the electronic control port provides configuration information for the optical control signal. In some embodiments, a processor in the optical network element provides configuration information for the optical control signal. In some embodiments, the configuration information for the transmitted optical control signal provided by the processor in the optical network element is generated based on the received optical control signal.

[0111] In one embodiment of the present teachings, the optical components of the hardware configuration include a counter-propagating Raman pump unit and a variable-gain (VG) optical amplifier (such as a VGA). The Raman pump unit and the VGA can be integrated to provide very low noise figures and excellent gain flatness, which are highly desirable characteristics for ultra-long-range optical communication systems. In various configurations, the existing optical amplifier module can currently support up to three Raman / EDFA pumped optical amplifiers in various configurations.

[0112] In embodiments using a Raman pump cell and a variable gain optical amplifier, a fast automatic gain control (AGC) circuit can be used to provide a high degree of transient suppression, which allows the optical amplifier to maintain constant gain during operating conditions in the presence of rapid and large changes in input power that are independent of the amplified stimulated emission (ASE) generated by the Raman pump optical amplifier. Suitable variable gain two-stage erbium-doped fiber amplifiers that provide flat gain across the C-band with low noise figures and a large dynamic gain range (up to 15 dB) are commercially available from Finisar Corporation. In some embodiments, the optical amplifier includes various features such as integrated transient control, tunable mid-stage access (MSA) loss, and gain tilt functionality, all of which can be used together or separately to control the attenuation through the device to impose low-frequency modulation on an existing optical signal.

[0113] A feature of the present teachings is that hardware-configured optical components provide a means for transmitting configuration information to components in a network comprising numerous hardware-configured optical components. The methods and apparatus of the present teachings are compatible with existing deployed optical components in known networks and can be readily implemented using known low-frequency modulation techniques and known information processing methods. Compatible existing networks include industry-standard data communication and telecommunications networks, such as large service provider networks and enterprise networks, as well as private networks and purpose-built network systems, such as those used for industrial control. In some embodiments of the present teachings, configuration information or control signals are exchanged between optical components in a point-to-point manner. In other embodiments, configuration information is exchanged between optical components in a broadcast or multicast manner for some or all optical components on the network. In other embodiments, configuration information is exchanged in a multipoint or cascaded manner. In various embodiments, any combination of these methods for exchanging configuration information or control signal information between optical components can be used.

[0114] Another feature of a hardware-configured network of optical elements including the hardware-configured optical elements of the present teachings is that known communication protocols and known management information protocols can be used to configure network elements. That is, known rule systems for collecting information from network elements and configuring network elements can be used. These protocols include data communication, telecommunications transmission, and management protocols for managing data formats, addressing, routing, error and fault management, flow and sequence control, and other known management elements and functions. In various embodiments, these protocols include embedded systems, real-time systems, and computer bus protocols.

[0115] Figure 5 An oscilloscope trace showing a low frequency control signal 500 according to the present teachings including a collision avoidance protocol based on a modification of the well-known Ethernet protocol. Figure 5The low-frequency control signal 500 shown in FIG. includes a protocol suitable for multipoint communication. Encoded control information is transmitted in "bursts," shown as regions 502 and 502', where modulated "1s" and "0s" appear on client data traffic 504. The duration of the burst, shown as time t 506, is small compared to the retransmission time T 508. In some embodiments, the ratio t / T is 0.1, so that the packet time is only 10% of the retransmission time. Each transceiver uses a random percentage of the retransmission time for the packet burst to avoid possible collisions between packets sent from different transmitters and improve decoding reliability at the receiver. In other words, the t / T ratio for the various transmitters is randomly selected.

[0116] One aspect of the present teachings is that the optical components of a hardware-configured network can be arranged in any network configuration, including mesh, point-to-point, ring, bus, tree, and other known structures. Furthermore, the optical components of a hardware-configured network of the present teachings can include several different component types, including transceivers, amplifiers, optical channel monitors (OCMs), wavelength selective switches, wavelength division multiplexing (WDM) multiplexers and demultiplexers, cross-connects, and optical switches. Thus, the configuration system of the present teachings supports a wide range of network topologies, network sizes and scopes, and network services.

[0117] Another aspect of the present teachings is that different combinations of optical network elements (including transceivers, amplifiers, optical channel monitors, wavelength selective switches, multiplexers / demultiplexers, cross-connects, and optical switches) can be configured using the common configuration schemes described herein.

[0118] Figure 6 An embodiment of a network of hardware configurations of the present teachings is represented in a point-to-point transceiver topology (sometimes referred to in the art as an optical link). Figure 6 The point-to-point configuration shown in can be expanded to other more complex network topologies (such as meshes, rings, and buses) including additional optical transceiver elements. Figure 6 In the embodiment shown in FIG, two optical transceivers 602, 602' are connected via a single optical fiber 604, which is used to transmit information from the first transceiver 602 to the second transceiver 602'. A second optical fiber 606 transmits information from the second transceiver 602' to the first transceiver 602. In some embodiments, the optical link operates using a coherent optical signal format.

[0119] Transceivers 602 include control ports 608, 608' for sending and receiving command and control information signals. Each transceiver 602, 602' also includes ports 607, 607' for sending and receiving client data traffic. An oscilloscope trace of the measured output of the first transceiver 602 shows normal client data traffic 610 at a data rate of 10 Gb / s and low-frequency control signals 612. Note that the integrity of client data traffic 610 is not affected by low-frequency control signals 612. Figure 6 The low-frequency control signal 612 shown in FIG. 1 is an amplitude modulated signal, but those skilled in the art will appreciate that any modulation format can be used. The low-frequency control signal 612 includes control and management information transmitted from the first transceiver 602. A microprocessor in the second optical transceiver 602′ is used to decode the string of "1s" and "0s" received from the first optical transceiver 602. In this way, configuration information is shared from the first optical transceiver 602 to the second optical transceiver 602′.

[0120] A second optical fiber 606 is used to transmit configuration information from the second transceiver 602′ to the first transceiver 602. In this manner, configuration information is shared from the second optical transceiver 602′ to the first optical transceiver 602. The control ports 608, 608′ on the first and second transceivers 602, 602′ can include an industry-standard I2C interface or other type of communication interface. Thus, using the low-frequency modulation method currently taught, digital diagnostic information can be encoded, shared, and decoded in both directions between the two transceivers 602, 602′. There is no need for one or the other of the transceivers 602, 602′ to communicate with a separate control processor or management system to configure the link, as is done in prior art link configuration systems. In some embodiments, the low-frequency modulation is caused by wavelength tuning in one and / or the other transceiver 602, 602′. In these embodiments, the tuning across different wavelength channels causes a low-frequency detection signal to appear when a signal is detected at the input of the transceiver 602, 602′. Tuning through the wavelength channels occurs during various wavelength channel scans (eg, slow scans and fast scans of the wavelength channels) described in greater detail herein.

[0121] Hardware-configured links that operate autonomously without the need to communicate with a separate management system or controller can be extended to large optical systems. For example, a large wavelength-count optical link comprising a large number of transceivers can be configured using various embodiments of the methods and apparatus of the present teachings. Figure 71 shows an embodiment of a network 700 of the present teachings comprising a hardware configuration of a plurality of tunable optical transceivers 702, 702' connected to a wavelength selective switch or optical programmable filtering element 704. As with other embodiments described herein, the transceivers 702, 702' may include customer traffic ports. The wavelength selective switch can be used to route optical signals between optical fibers based on specific wavelengths or channels. The wavelength selective switch can be configured as a reconfigurable optical add / drop multiplexer and used as an automated patch panel to quickly move wavelengths and bandwidth to different optical fibers. For example, the Flexgrid 100 commercially available from Finisar Corporation TM The technology provides dynamic control of the channel center frequency with 6.25 GHz resolution and 12.5 GHz channel width resolution within the wavelength selective switch. TM Once deployed, the channel plan is configurable "on the fly," meaning that the channel bandwidth can be adjusted to most efficiently support future demands as they arise, or for any other purpose.

[0122] One example of a prior art programmable optical filter is the WaveShaper family of programmable light processors commercially available from Finisar Corporation.

[0123] Programmable optical filters offer a range of programmable optical filtering and switching, including very fine control of filter characteristics such as center wavelength, bandwidth, shape and dispersion, and attenuation. Programmable optical filters can provide a variety of functions such as tunable optical filtering, optical bandwidth management, dynamic gain equalization, programmable optical filtering, polarization processing, and multi-port optical processing. Using the hardware-configured network methods and devices of the present teachings, all of these parameters of wavelength selective switches and programmable optical filters can be configured.

[0124] Figure 7 Two optical transceivers 702 and 702' are shown, each having an optical output connected to an input of a programmable filtering element 704 using optical fibers 706 and 706'. In some embodiments, the optical connection between the two transceivers 702 and 702' and the programmable filtering element 704 can be bidirectional. The programmable filtering element 704 includes an output optically connected to an output fiber 708 and an electronic control port 710 for receiving electronic control signals. The two optical transceivers 702 and 702' have electronic control ports 712 and 714 for receiving the electronic control signals.

[0125] In some embodiments, the optical transceivers 702, 702' are tunable and configured to transmit and receive different wavelength channels. Figure 7In the configuration shown in , programmable filtering element 704 is programmed to receive two wavelength channels and transmit the two wavelength channels on output fiber 708. Those skilled in the art will appreciate that any number of transceivers having any number of channels can be used with the methods and apparatus of the present teachings.

[0126] In some embodiments, a local client 716 is used to provide control information to configure the programmable filter element 704 and set wavelength channels from transceivers 702 and 702'. In some embodiments, control information is independently provided from an external source using control ports 710, 712, and 714. The control information is encoded on a low-frequency control signal, which is applied to the existing optical signal propagating on optical fibers 706, 706', and 708. In this way, information for component configuration is transmitted over the network. In some embodiments, both local client-based and independent input methods are used. In various embodiments, the local client may or may not be co-located with the optical element. In various embodiments, the local client is pre-programmed to, for example, automatically activate components and provide other local control information so that the components (e.g., transceivers 702, 702' and / or WSS or programmable filter 704) can operate autonomously without requiring an external management system or controller to activate and / or configure the link.

[0127] Figure 8 An embodiment of a network 800 of the present teachings, including a hardware configuration of a wavelength division multiplexing network with wavelength selective switch optical elements, is shown. Many known network element configurations rely on the use of clients to transmit configuration information to various elements in the wavelength division multiplexing network using separate "supervision" channels. A feature of the hardware-configured network of the present teachings is that known client hardware is no longer required to provide element configuration. Client hardware and other external management systems can be provided and used in the network, but are no longer required for element configuration. Furthermore, if such client hardware and other external management systems are used, their role can be greatly reduced. Instead, as described herein, configuration information is provided via low-frequency control signals applied to existing optical signals in the optical network.

[0128] Figure 8804. The diagram shows first and second transceivers 802, 802' having bidirectional optical ports optically coupled to an add wavelength selective switch 804 using optical fibers 806, 806'. In some embodiments, bidirectional communication exists between the first and second transceivers 802, 802' and the add wavelength selective switch 804. In other embodiments, only unidirectional communication exists from the first and second transceivers 802, 802' to the add wavelength selective switch 804. The transceivers 802, 802' also include control ports 808, 808' for receiving control information.

[0129] The add wavelength selective switch 804 has an electrical control port 810 for receiving control information. In some embodiments, the electrical control port 810 is not used, and the control information is provided via optical fibers 806 and 806'. Furthermore, the add wavelength selective switch 804 includes an optical bidirectional port that is optically coupled to a bidirectional port of a demultiplexing wavelength selective switch 814 using optical fiber 812. The demultiplexing wavelength selective switch 814 has an electrical control port 816 for receiving control information. In operation, the add wavelength selective switch 804 can be configured to controllably connect various wavelengths from various input ports to specific output ports. The demultiplexing wavelength selective switch 814 can also be configured to controllably connect various wavelengths from specific input ports to one or more of the various output ports. Those skilled in the art will appreciate that the add wavelength selective switch 804 and the demultiplexing wavelength selective switch 814 can also operate in the reverse direction, such that the add wavelength selective switch 804 becomes a demultiplexing wavelength selective switch, and vice versa.

[0130] The wavelength selective switch 814 also includes two bidirectional ports that are optically coupled to first and second optical fibers 818, 818'. In the embodiment shown, the optical fibers 818, 818' transmit the optical signals from the wavelength selective switch 814 to transceivers 820, 820'. The transceivers 820, 820' have electrical control ports 822, 822'. Figure 8 In the embodiment shown in FIG, transceivers 802 and 802' transmit signals to a wavelength selective switch 814 through an add wavelength selective switch 804, which transmits signals to transceivers 820 and 820', which receive signals. With respect to other embodiments described herein, transceivers 802, 802', 820, and 820' may include client data traffic ports.

[0131] exist Figure 8In the embodiment shown in FIG, transceiver 802 at position A 824 is in transmit mode and optically coupled to transceiver 820, which is in receive mode at position B 826. Similarly, transceiver 802′ at position A 824 is in transmit mode and connected to transceiver 820′ at position B 826, which is in receive mode. In one method of operation, transceiver 802 is configured, at least in part, using client configuration device 828, to provide data on a particular wavelength channel.

[0132] Using low-frequency modulation, encoded control information is applied to a wavelength channel originating from transceiver 802 and sent to add wavelength selective switch 804. The encoded control information is received by add wavelength selective switch 804, decoded, and used to configure add wavelength selective switch 804 to transmit the signal from transceiver 802 to output fiber 812, which is connected to demultiplexing wavelength selective switch 814. This action causes the control signal to be transmitted to demultiplexing wavelength selective switch 814, where it is then decoded. Demultiplexing wavelength selective switch 814 then uses the decoded control information to configure demultiplexing wavelength selective switch 814 to transmit the signal from transceiver 802 to optical fiber 818. This configuration of demultiplexing wavelength selective switch 814 thus transmits the signal originating from transceiver 802 and the encoded control information to receiver 820. The encoded control information is received at transceiver 820 and used to configure transceiver 820 to receive the signal data from transceiver 802.

[0133] In some embodiments, one or more optical channel monitors 830, 832 provide control information to the hardware-configurable add wavelength switch 804 and drop wavelength switch 814. The optical channel monitors 830, 832 monitor the details of the optical signals passing through the add wavelength selective switch 804 or drop wavelength selective switch 814, or both, and use this information to notify the hardware-configured network of various control actions. The control actions are signaled to the network via the low-frequency modulation encoding described herein. As described above, the elements in the hardware-configured network are thus able to automatically configure and / or otherwise manage and control the connectivity of the hardware-configured network.

[0134] Those skilled in the art will appreciate that the add wavelength selective switch 804 and the drop wavelength selective switch 814 are capable of running traffic in both the forward and reverse directions simultaneously. However, two optical fibers between each element are required to propagate traffic in both directions and can be configured for bidirectional transceivers for client traffic.

[0135] Those skilled in the art will understand that Figure 8The specific sequence of events for automatically configuring and providing a hardware-configured network is illustrative and does not limit the present teachings in any way. For example, various protocols can be used to establish network connectivity and network configuration between optical components using the low-frequency control signals described herein in various sequences. Furthermore, a client can be used to provide electronic control signals to any element in the network for any or all configuration events. Furthermore, a client can be used to initiate one or more configuration events, and the automatically encoded information can be used for the remainder of the configuration events.

[0136] One aspect of the present teachings is the ability to automatically detect installation errors without the use of a client or external network manager. Installation errors cause the actual deployed hardware physical connections to deviate from the planned hardware physical connections. The term "physical connection" herein refers to the connection of a specific port of one or more optical components to a specific port on a specific fiber or optical component. When an installation error occurs, the planned component configuration pre-programmed into the optical components using the planned hardware physical connections will not result in the proper optical signal path between the components. In known configuration systems, the only way to recover from an installation error is to use expensive human intervention to both detect the incorrect connection and redeploy the hardware to establish the planned hardware physical connections.

[0137] Figure 9 express Figure 8 Figure 9 is a network 900 with a hardware configuration in which the wiring was incorrectly installed at location B. The installation error caused a cross-wiring condition at location B 902. The planned wiring connections required receiving transceiver RX-1 904 to be connected to optical fiber 906 and receiving transceiver RX-2 908 to be connected to optical fiber 910. The installer error caused receiving transceiver RX-1 904 to be connected to optical fiber 910 and receiving transceiver RX-2 908 to be connected to optical fiber 906, as shown in Figure 9. Figure 9As shown in . Unfortunately, for telecommunications service providers, such installation errors often occur and cause significant service startup delays and increased costs. Even with systems configured using prior art network hardware, cross-wiring conditions are difficult to detect and correct. Detecting an installation error condition requires the use of a human operator to correlate the error conditions across multiple network elements, followed by a subsequent service call by a field technician to locate the equipment and reconnect it to its intended physical connection. For example, in a system where a transceiver port is intentionally or accidentally swapped to a different channel, the different connected channels can be identified by the connected transceiver, which can be a client. The filters connected to the client can be determined by polling the connected transceiver. In some embodiments, detected client data traffic can be used to provide additional troubleshooting information, but the frames modulated at a low frequency need to be decoded and compared. A simple low-speed polling of the connected channel via the debug port will indicate an error.

[0138] Network devices and methods using the hardware configurations of this teaching, Figure 9 Cross-wiring installation errors can be automatically detected and corrected with minimal human intervention or truck rolls. Specifically, initially, the wavelength selective switch 912 transmits an optical signal including a low-frequency control signal according to the present teachings from transmitting transceiver TX-1 916 at location A 914 to receiving transceiver RX-2 908 at location B 902. Receiving transceiver RX-2 908 at location B 902 identifies a connection error because the configuration information encoded on the low-frequency control signal comes from TX-1 916 at location A 914 rather than from TX-2 918 at location A 914 as expected. Receiving transceiver RX-2 908 at location B 902 then initiates corrective action by encoding the corrective configuration information on the low-frequency control signal that is directed to the appropriate network element to provide corrective action to mitigate the installation error.

[0139] Specifically, reconfiguration of the wavelength selective switch 912 is used to correct wiring errors. Reconfiguration is initiated by coded information sent from the receiving transceiver RX-2 908 at location B 902 to the wavelength selective switch 912 at location B 902 to reconfigure the sub-channels so that RX-2 908 at location B 902 receives optical signals from TX-2 918 at location A 914. Thus, the wavelength selective switch 912 is reconfigured based on the control information sent from the receiving transceiver RX-2 908 so that the signal from TX-1 916 at location A 914 appears on the deployed optical fiber 910 instead of the planned optical fiber 906, and the signal from TX-2 918 at location A 914 appears on the deployed optical fiber 906 instead of the planned optical fiber 908. In this way, the reconfiguration of optical components in a hardware-configured network of the present teachings corrects installation errors without expensive human intervention. The ramifications for other installation errors and the necessary reconfiguration steps are well understood by those familiar with the prior art of network configuration and failure recovery.

[0140] One aspect of the present teachings is the ability to catch installation errors earlier on the sending side of the network, rather than detecting configuration errors only at the receiving end of the network after the signal arrives, as is currently performed in known systems. Figure 10 express Figure 8FIGURE 1 illustrates a network 1000 with a hardware configuration in which an installer made an error when routing components at location A 1002. Specifically, optical fiber 1004 originating from transmitting transceiver TX-1 1006 was connected to input 1008 on add / drop wavelength selective switch 1010, which was actually intended for optical fiber transceiver TX-2 1012. Furthermore, optical fiber 1014 originating from transmitting transceiver TX-2 1012 was connected to input 1016 on add / drop wavelength selective switch 1010, which was intended for transceiver TX-1 1006. In other words, due to an installation error, the connections from transceivers 1006 and 1012 to add / drop wavelength selective switch 1010 on inputs 1008 and 1016 were swapped relative to the intended deployment. In this misconfiguration, the add wavelength selective switch 1010, which was initially configured to route a signal appearing on input 1016 from transmitting transceiver TX-1 1006, instead receives a signal on that port 1016 from transceiver TX-2 1012. The encoded configuration information provided on the low-frequency control signal detected by the add wavelength selective switch 1010 enables this error to be immediately detected within the add wavelength selective switch 1010. In some operating methods, the error can be corrected by having the hardware-configured network notify a client or third-party administrator that wiring needs to be repaired. In other automated operating methods, the hardware-configured network automatically reconfigures the transceivers 1006, 1012, or automatically reconfigures the add wavelength selective switch 1010. Automatic reconfiguration is initiated based on control information sent to the optical element, which can be reconfigured to correct the error from the optical element that detected the error.

[0141] One aspect of the present teachings is the ability to provide a low-cost multi-transceiver combiner-splitter. Figure 11 1 shows an embodiment of a low-cost combiner-splitter 1100 comprising hardware-configured elements according to the present teachings. A plurality of transceivers 1102, 1102' are connected to a passive combiner 1106 using a plurality of optical fibers 1104, 1104'. The passive combiner 1106 can include any number of ports. For example, the passive combiner 1106 can be a sixteen-port (16:1) passive combiner. By passive combiner, we mean a combiner without filtering capabilities for filtering individual wavelength channels, although in some embodiments, some other type of wavelength filtering can occur in the passive combiner elements.

[0142] The output of passive combiner 1106 is optically coupled to optical amplifier 1110 using optical fiber 1108. Optical amplifier 1110 is used to overcome the loss of combiner 1106, which is approximately 13 dB for a 16:1 combiner. Optical amplifier 1110 can be a widely available, low-cost erbium-doped fiber amplifier. For example, in one embodiment, optical amplifier 1110 has a startup power of 0 dBm for each transceiver 1102, 1102' and sufficient amplifier gain to overcome combiner loss, resulting in an output power of 12 dBm. The output of optical amplifier 1110 is optically coupled to optical splitter-combiner 1114 using optical fiber 1112. Optical splitter-combiner 1114 includes multiple optical outputs 1116, 1116', which are optically coupled to multiple transceivers 1118, 1118'.

[0143] In various embodiments, transceivers 1102, 1102' and transceivers 1118, 1118' operate in either transmit or receive mode. For example, in one method of operation, transceivers 1102, 1102' operate in transmit mode and transceivers 1118, 1118' operate in receive mode. In another method of operation, transceivers 1102, 1102' operate in receive mode and transceivers 1118, 1118' operate in transmit mode.

[0144] Some or all of the transceivers 1102, 1102', transceivers 1118, 1118', and amplifier 1110 are configured using the low-frequency modulation described herein. One feature of the hardware-configured network of the present teachings is that there is no need to track fiber order or mark specific transceiver connections, as all configuration information can be provided by the low-frequency control signals. The configuration information allows for the automatic provision of tunable channels and the establishment of all data connections between the transceivers.

[0145] One aspect of the present teachings is that a network of the hardware configurations described herein can provide digital diagnostics for optical network components. Known transceivers sometimes include a microprocessor and a diagnostic interface that provides performance information about the data link. This allows users to remotely monitor, in real time, a number of performance parameters for any transceiver in the network, such as received optical power, transmitted optical power, laser bias current, transceiver input voltage, and transceiver temperature. The digital diagnostic functionality provides users, clients, and external network management systems with tools for implementing performance monitoring.

[0146] Some known optical transceivers provide digital diagnostics via a digital diagnostic monitoring interface (DDMI). The DDMI specifies control information that is transmitted to a client or external management system and includes information such as component identification information, component operating parameters, network and component configuration information, alarm and warning parameters, and vendor information. Finisar Corporation application note AN-2030, "Digital Diagnostic Monitoring Interface for Optical Transceivers," details a digital diagnostic monitoring interface for small form factor (SFP) optical transceivers.

[0147] Known digital diagnostic monitoring interfaces include an interface device or optical transceiver that provides real-time access to device operating parameters, as well as alarm and warning flags that alert the user when operating parameters are outside of normal ranges. Known digital diagnostic monitoring interface devices generate diagnostic data by digitizing internally monitored analog signals. Calibration and alarm threshold data are typically programmed during the interface device's manufacture. In addition to generating digital readouts of internal analog values, known digital diagnostic monitoring interface devices also generate various status bits based on comparisons with current values ​​and factory preset values. Furthermore, known digital diagnostic monitoring interface devices generate identifier information.

[0148] Another aspect of the hardware-configured network of the present teachings is the provision of enhanced digital diagnostic monitoring. Some embodiments of the hardware-configured network of the present teachings provide digital diagnostic monitoring interface control information as part of the low-frequency control signal described herein. In particular, the low-frequency control information can include a data field that is part of the low-frequency control signal described herein and provides specific information about the transmitter component of the transceiver element. For example, the low-frequency information signal can include one or more transmitter serial numbers of the transceiver element comprising the transmitter and / or a transmitter channel identification number for a specific transceiver element. The transmitter channel identification number provides the wavelength and / or channel number to which the laser transmitter is tuned. The low-frequency information signal described herein can also include information about the receiver component of the transceiver element. For example, the low-frequency information signal can include one or more receiver serial numbers of the transceiver element comprising the receiver and / or a receiver channel identification number for a specific transceiver element.

[0149] Another aspect of the hardware-configured network of the present teachings is that it is capable of providing enhanced digital diagnostics by exchanging configuration information with components such as transceivers, amplifiers, wavelength filters, optical channel monitors, wavelength selective switches, wavelength multiplexers, wavelength demultiplexers, cross-connects, and optical switches. The enhanced digital diagnostic information is used as control information encoded on the optical control signals of the present teachings. Compared to prior art configured systems, the use of optical control signals of the present teachings provides additional flexibility in the ability to reach various optical components in the hardware-configured network by selecting appropriate optical carriers. In some embodiments of the hardware-configured network of the present teachings, the hardware-configurable elements include photodiodes that decode the low-frequency control signals described herein.

[0150] Those skilled in the art will appreciate that hardware-configurable components according to the present teachings can be used for a variety of purposes. For example, in some embodiments, a hardware-configurable optical amplifier can be configured for network discovery prior to transceiver transmitter operation. Furthermore, in some embodiments, the hardware-configurable amplifier can be configured to have an optical gain that is calculated based on optical path noise. Furthermore, in some embodiments, the hardware-configurable amplifier gain profile is adjusted based on channel activation of a remote transceiver. Furthermore, in some embodiments, the hardware-configurable amplifier can transmit information regarding the optical gain to the transceiver.

[0151] Furthermore, in some embodiments, hardware-configurable wavelength selective switch ports are configured and reconfigured as needed based on data traffic using flexible channel planning. Furthermore, in some embodiments, hardware-configurable wavelength selective switches are used to provide network protection against failures by reconfiguring optical paths in the network after a failure. Furthermore, in some embodiments, hardware-configurable optical programmable filters automatically adjust path dispersion based on performance information provided by hardware-configurable transceiver elements without requiring user or external network management intervention.

[0152] Furthermore, in some embodiments, the low frequency control signals described herein are used to calibrate a hardware configurable optical channel monitor. Figure 8 By adding precision channel monitors 830, 832 and using enhanced digital diagnostic control information in a network of hardware configurations of the present teachings, transceivers used in the network can be tuned and more closely spaced for higher overall optical transmission rates and spectral efficiency.

[0153] A feature of the present teaching is that network elements configured according to the hardware configuration of the present teaching can be configured without using amplitude-modulated control signals on the optical carrier. Specifically, changes to the optical carrier can be utilized that are simply generated by actions taken during the configuration protocol. These changes in the optical signal based on protocol-driven actions in the control processor are identified at appropriate downstream devices or components as part of the network configuration, and information derived from these changes identified in the optical signal is used to close the configuration loop for a specific predetermined configuration. For example, the fact that a transmitter is turned on and / or the duration and / or power level of the transmitter's on time can be monitored and determined at an element (e.g., a downstream receiver). The determined state of the transmitter derived by the downstream receiver and the monitored optical signal are then used as part of the information for managing and controlling the network. For example, the network may include a transmitter, a receiver, and one or more elements connecting the transmitter and the receiver. Any of the downstream elements of the transmitter can monitor the changes to the optical carrier generated by the configuration changes.

[0154] The benefit of building a configuration protocol from signals that are caused only by configuration changes of the components themselves is that there is no need for framing, additional traffic bandwidth, or complex control signaling or encoding of the optical signals used for configuration. Changes in the optical signals caused by the normal function of a particular component (e.g., turning it on or off or changing wavelength) are independent of any framing, traffic, or other modulated control signals. In the case of turning a transmitter on or off, the presence or absence of light may be all that is needed to control channel switching and configuration. In embodiments where the transmitter is a tunable transmitter, the speed at which these signals change can be as fast as the tuning speed of the transmitter. In this way, a hardware-configured network can change and / or determine its operating state and approach the final configuration very quickly.

[0155] Figure 12AA block diagram illustrates an embodiment of a hardware-configurable link 1200 including a hardware-configured tunable transceiver according to the present teachings. Link 1200 can operate in both directions, but only a single direction is shown. Two transceivers 1202 and 1204 are shown transmitting at the near end of link 1200. Each transceiver 1202 and 1204 generates an optical signal on an optical carrier at a specific wavelength channel. The output of transceivers 1202 and 1204 is input to a WDM combiner 1206 and transmitted to the far end of the link over a delivery fiber 1208. The fiber connection between transceivers 1202 and 1204 and WDM combiner 1206 can be relatively long, in some embodiments, up to 2 km in length. The signal from delivery fiber 1208 is separated at a WDM splitter 1210, and the different wavelength channels are transmitted to specific transceivers 1212 and 1214 that receive optical signals on specific channels based on the WDM configuration. Transceivers 1202, 1204, 1212, 1214 are thus interconnected with a low-cost WDM splitter 1210 and combiner 1206. One feature is that there is no need to track the specific order of connecting fibers 1216, 1218, 1220, 1222 in order to configure link 1200. Tunable channels can be deployed, and connections and traffic between transceivers 1202, 1204, 1212, 1214 can be established without additional optical channels for control. In some embodiments, transceivers 1202, 1204, 1212, 1214 are tunable coherent transceivers.

[0156] Figure 12B Indicates that it can be combined with Figure 12A 12. A block diagram of an embodiment of a transceiver according to the present teachings for use with a hardware-configurable link is shown. A transmitter 1232 and a receiver 1234 are controlled by a processor 1236. The transmitter 1232 is connected to a transmit fiber 1238, and the receiver 1234 is connected to a receive fiber 1240. In some embodiments, the transmit fiber 1238 and the receive fiber 1240 are connected to a WDM multiplexer / demultiplexer that can be collocated with the transceiver 1202 or located remotely.

[0157] Can be used to configure Figure 12AAn embodiment of a control protocol according to the present teachings for a link configured with a hardware configuration of -B is as follows. Upon power-up, in the near-end transceiver 1202, the transmitter in transceiver 1202 turns on and begins a slow channel change. During this slow scan, the transmitter generates an optical signal that sequentially steps through all channels in the system. Each wavelength channel is transmitted using a dwell time on a particular wavelength channel. The dwell time is the time the transmitter generates the wavelength of a particular channel during the channel scan. Each complete scan includes transmission from the transmitter using the dwell time on each wavelength channel of the system. The system typically begins scanning on the first wavelength channel, but in some cases, other orders are used, and / or the scan may begin on the next channel after the last channel transmitted. This may occur, for example, if the scan is interrupted for some reason. Some embodiments include intervals between dwell times on a particular wavelength channel, while some embodiments operate with nominally no intervals between dwell times on a particular wavelength channel. The receiver at the far-end transceiver 1212 waits for a signal. The signal will be detected, for example, when a portion of the signal generated by transceiver 1202 that includes the slow scan is detected in transceiver 1212. In various embodiments, the receiver in transceiver 1212 can determine the state of transceiver 1202 on the other side of the link based on the duration of the received signal as described herein.

[0158] When the receiver at far-end transceiver 1212 senses an optical signal from the near-end transmitter because the transmitter at near-end transceiver 1202 has tuned to the correct channel, the transmitter in far-end transceiver 1212 enters a rapid scan mode. During a rapid scan, the transmitter generates an optical signal that sequentially steps through all channels in the system. Each wavelength channel is transmitted using a dwell time on a specific wavelength channel. For rapid scans, these transmissions can be referred to as short pulses. The duration of the dwell time on a specific wavelength channel is much shorter than the duration of the slow scan dwell time on a specific wavelength channel because the rapid scan is timed to completely traverse the wavelength channels in the scanning system in a time that is shorter than the individual channel dwell time of the slow scan wavelength channel. In other words, the total channel scan time for the rapid scan is the same duration as, or shorter than, the dwell time on a specific wavelength channel for the slow scan. The rapid tuning of the transmitter channel in the far-end transceiver 1212 during the rapid scan makes it possible to connect the link back to the other end because the receiver in the near-end transceiver 1202 senses the signal from the far-end rapidly tuned transmitter while the wavelength is tuned to the appropriate channel. That is, the transceiver 1202 detects a short duration signal whose duration is nominally equal to the dwell time on the particular channel of the rapid scan. The near-end transceiver 1202 remains tuned to the channel it is transmitting from while sensing the signal from the far-end rapidly tuned transmitter because that channel is appropriate for connection to the far-end receiver. The near-end transceiver 1202 can now use the current operating wavelength channel to transmit traffic over the link. The receiver in the far-end transceiver 1212 can be used to initiate any subsequent configuration, including, for example, the setup of the link in the reverse direction. The link setup protocol can operate in either direction. Although Figure 12A The block diagram of transceiver 1202 shows a transceiver transmitter and receiver, each connected to separate transmit and receive optical fibers, but it is straightforward for one skilled in the art to apply the described protocol to many types of bidirectional transceivers and optical fiber connections.

[0159] Some embodiments of the protocol for configuring hardware-configurable links of the present teachings use a limited set of possible transmitter states to help simplify the required processing. These transmitter states include TX_SLOW_TUNE, in which a tunable laser in the transceiver is tuned to change channels at a rate of one second per channel, enabling slow scanning. In various embodiments, various slow rates are used. The TX_FAST_TUNE state utilizes a faster wavelength tuning mechanism to achieve fast channel changes using a channel plan with a 10ms dwell time per channel, enabling fast scanning. TX_FAST_TUNE operates within + / - 5 GHz from the ITU channel grid within a 10ms duration. Other sweep speeds and wavelength accuracies may be used depending on the specific application. In some basic embodiments, the transceiver only needs to detect and determine the dwell time from a specific wavelength for the slow scan and the dwell time from a specific wavelength for the fast scan to complete link setup and transmit client traffic over the link. In some embodiments, additional states are used that generate optical signals using other timings that can be distinguished by detectors in the transceiver. State TX_BEACON is a state in which the laser is powered on for a dwell time shorter than the slow scan dwell time but longer than the fast scan dwell time, followed by a power-off period of the same duration. For example, TX_BEACON may be a laser power-on dwell time that is half the duration of the slow scan dwell time on a particular channel. In some embodiments, the TX_BEACON state uses a channel power-on period of 0.5 seconds and a channel power-off period of 0.5 seconds for the currently operating wavelength channel. The TX_BEACON state will switch between power-on and power-off until the state in the transmitter changes. The TX_HOLD state maintains the laser power input and on state for the currently operating specific wavelength channel. These states are used by the processor to control the output of the transmitter. Generally speaking, the transmitter will remain in a specific state until that state is changed by the processor.

[0160] Figure 13A graph 1300 showing optical power as a function of time is shown for an embodiment of a set of transmitter states 1302, 1304, 1306, and 1308 according to the present teachings. TX_SLOW_TUNE 1302 cycles through the following state tuning: power is transmitted in channel 1 1310, then in channel 2 1312, and so on until it is transmitted in channel 40 1314, then starting again at channel 1 1316. TX_SLOW_TUNE 1302 is an embodiment of a slow scan of wavelength channels. Power is generated in approximately one second per channel. In other words, the dwell time on a particular channel in the scan has a duration of one second. TX_FAST_TUNE 1304 generates power in all 40 channels over a 400 ms period 1318. Power is generated in approximately 10 ms per channel. TX_FAST_TUNE 1304 is an example of a fast scan of wavelength channels, where the dwell time on a particular channel in the fast scan has a duration of 10 ms. TX_BEACON 1306 generates power in the currently tuned channel during approximately 50 ms on-duration 1302 and 50 ms off-duration 1322. State TX_HOLD continuously generates optical power 1324 in the current channel.

[0161] Some embodiments of the protocol for configuring a hardware-configurable link according to the present teachings use a limited set of possible receiver states. These include RX_ON, in which the power measured by the receiver is determined to be greater than a specified threshold for a period greater than 8 milliseconds. In some embodiments, this threshold is a power threshold and is the same as the receiver's power threshold for protection events. In some embodiments, the threshold includes a duration threshold, and the power-on duration is determined to exceed the threshold when the duration is determined to be greater than a specified duration. In some embodiments, the power-on duration is determined to exceed the threshold when the duration is determined to be less than a specified duration. State RX_10MS is a state in which the receiver determines that it has received light for a period greater than 8 milliseconds. RX_1SEC is a state in which the receiver determines that it has received light for a period greater than 1 second. RX_BEACON is a state in which the receiver determines that it has received light-on for a period of 0.5 seconds, followed by light-off for a period of 0.5 seconds. The durations used for various receiver states may vary in different embodiments. Generally speaking, it is important that the receiver can distinguish between a long-duration light-on state, a short-duration light-on state, and a light-on / light-off state to implement embodiments of the link configuration protocol.

[0162] A feature of the present teachings is that a bidirectional link configuration protocol can be established without having to implement two unidirectional setup protocols. For example, to enable multipoint communication to a specific receiver in bidirectional mode, some embodiments of the present teachings utilize the following algorithm. Note that this algorithm description assumes that transceiver A is located at the near end of the link and includes transmitter A and receiver A. Transceiver B is located at the far end of the link and includes transmitter B and receiver B. The algorithm proceeds as follows: (1) After power-up, transmitter A turns on to start on channel 1 of a particular channel plan; (2) transmitter A dwells on channel 1 for one second and progresses through channel changes at a rate of 1 second / channel (in other words, transmitter A generates a slow scan, where the slow scan has a dwell time on a particular wavelength channel that is greater than the duration of the full channel scan of the fast scan, which is described in more detail in step 5); (3) when transmitter A tunes to a channel that reaches receiver B via the link (so that receiver B detects a portion of the first optical signal sent via the link that has a dwell time duration of the particular channel of the slow scan), transceiver B (the remote receiver) receives power; (4) remote transmitter B enters the fast tuning channel 1-N (e.g., N=40); (5) remote transmitter B traverses all N channels for fast tuning (changing In other words, transmitter B generates a fast scan in which a full channel scan is a scan that traverses all N channels of the system); (6) When transmitter B tunes to a channel arriving at receiver A, receiver A detects light from transmitter B during the fast channel tuning period (in other words, receiver A detects a pulse of light of a duration equal to or less than the dwell time on the particular wavelength channel of the fast scan); (7) transmitter A enters the hold condition on the channel currently being transmitted to receiver B; (8) transmitter A enters beacon mode; (9) receiver B detects the beacon from transmitter A; (10) transmitter B enters slow tuning; (11) receiver A detects a slow channel change from light from transmitter B; (12) transmitter A enters hold; (13) receiver B transitions from transmitter A detection state, beacon to hold; (14) transmitter B enters the hold condition; (15) the bidirectional link is complete. Transceiver A and transceiver B can then transmit client traffic bidirectionally.

[0163] This sequence is executed without any predetermined specific framing or sequencing at the far-end or near-end transceiver. Furthermore, no channels are predetermined. As such, the system is completely self-configuring, and the setup is completely independent of the specific fiber connection pattern established when the system was wired. Transceivers are able to discover each other and establish links without predetermined setup configuration information.

[0164] Figure 14A graph 1400 showing optical power as a function of time is shown for a set of transmitter and receiver states present during an embodiment of a method for connecting a protocol according to the present teachings. In this graph, the near-end transceiver is hardwired to the far-end transceiver via a WDN combiner and splitter so that channel 3 is the connecting channel. The graph shows a transmit optical signal 1402 generated by the near-end transmitter, a receive optical signal 1404 received at the far-end receiver, a transmit optical signal 1406 generated by the far-end transmitter, and a receive optical signal 1408 received at the near-end receiver. The near-end transmitter turns on and begins TX_SLOW_TUNE state 1410, tuning upwards from channel 1 at a rate of one second per channel. Generally, as shown, if state 1424 is entered, there is no need to restart at channel 1. In some embodiments, the slow scan instead continues from the last channel transmitted over the link. When the transceiver tunes to channel 3, a signal 1412 is detected at the far-end receiver. This causes the transmitter in the far-end transceiver to implement TX_FAST_TUNE 1414 (fast scanning). When channel 3 is transmitted to the receiver in the near-end transceiver, a received signal 1416 is detected at the near-end receiver. This causes the transmitter in the near-end transceiver to move to the TX_HOLD state 1418 on channel 3. The transmitter in the near-end transceiver transitions to the TX_BEACON state 1420 on the same channel 3. This beacon state is detected 1422 by the receiver in the far-end transceiver, and the processor in the far-end transceiver determines that the far-end received signal has transitioned from hold to beacon. This causes the transmitter in the far-end transceiver to initiate TX_SLOW_TUNE 1424. When the receiver in the near-end transceiver tunes to channel 3 1426, it detects an optical signal transmitted from the far-end transmitter. The processor in the near-end transceiver determines from this received signal that a threshold has been crossed and moves the transmitter in the near-end transceiver to hold 1428 on channel 3. The transition from beacon to hold 1430 is detected by the receiver in the remote transmitter, and the transition is determined by the processor in the remote transceiver, which then directs the remote transmitter to hold 1432 on channel 3. A bidirectional link is now established, and traffic can flow in both directions.

[0165] Therefore, in some embodiments, the reverse direction of the link is set autonomously, without separate control signaling, by generating a beacon signal at the near-end transceiver and transmitting it to the far-end transceiver via a WDM optical transport interconnect. The far-end transceiver receives a portion of the beacon signal. This causes the far-end transceiver to perform a wavelength channel scan in response to receiving the transmitted beacon signal. In some embodiments, the wavelength channel scan is a slow scan, potentially at a rate of one channel per second. While the channels via the WDM interconnect are being tuned, the near-end transceiver receives a portion of the optical signal generated by the far-end transceiver. When a processor in the near-end transceiver determines that the received portion of the signal exceeds a threshold, it generates a hold signal at the near-end transceiver. In other words, the near-end transceiver is caused to generate a continuous-time signal at the current operating wavelength, rather than the previous on-and-off beacon signal. The hold signal is detected by the far-end transceiver, and based on the power and / or duration of the received signal, it is determined to be a hold signal. The processor in the far-end transceiver then sets the operating wavelength of the far-end transceiver to maintain its current operating wavelength. The real-time traffic is then transmitted from the far-end transceiver at the current operating wavelength. The operating wavelength of the signal from the near-end transceiver to the far-end transceiver can be the same as or different from the operating wavelength from the far-end transceiver to the near-end transceiver. The wavelength depends on the wavelength channel passband of the WDM interconnect connecting the near-end transceiver to the far-end transceiver.

[0166] In some embodiments, once the near-end transceiver enters the hold state 1418 , the near-end transceiver begins sending real-time traffic to the far-end transceiver and does not transition to the TX_BEACON state 1420 .

[0167] In some embodiments, the transceivers on both sides of the link run the same state machine and begin slow scanning after power-up. No master or slave side is required, just a single controller software. In these embodiments, it depends on which side hits the filter first. For such a system, taps are added for the low-probability event that both sides simultaneously tune to the appropriate filter. The transceiver then restarts at a random time greater than the slow scan rate.

[0168] Figure 15A flowchart illustrating an embodiment of a protocol for establishing a link using transceiver elements configured with hardware according to the present teachings. The transceiver can operate in various modulation formats, including coherent modulation formats. The transceiver receiver can include a coherent receiver. The transceiver can include an SFP, SFP+, and / or CFP2 / CFP4 transceiver. In some embodiments, the near-end transceiver is hardwired to the far-end transceiver via a WDM combiner and splitter so that a specific channel can be passed all the way through the link from the near-end transceiver to the far-end transceiver to establish the connection channel for the unidirectional connection. Similarly, in these embodiments, a specific channel can be passed all the way through the link from the far-end transceiver to the near-end transceiver to establish the connection channel for the unidirectional connection. Note that these channels can be the same, or they can be different. The specific connection channel is not necessarily known before startup. That is, in order to know in advance what channel will connect the near-end transceiver to the far-end transceiver and vice versa, it is not necessary to pay special attention to the hardwired fiber configuration. In other embodiments, the transceivers may be hardwired via passive splitter combiners to enable multiple channels to be passed between transceivers on a link. One advantage of the apparatus and methods of the present teachings is that configuration of the network and / or link is achieved without external human or management system intervention and relies on a configuration protocol based on signals caused solely by configuration changes in the elements themselves. That is, the configuration protocol in the methods and apparatus of the present teachings relies on low-frequency modulated control signals imparted on an optical carrier by the optical elements of the hardware-configured network.

[0169] In step 1 1502, the near-end and far-end transceivers are optically powered up. Generally, one or more transceiver pairs may be powered up. In step 2 1504, one of the transceivers, transceiver 1 (which, without loss of generality, may be referred to as the near-end transceiver), begins a slow wavelength scan as described herein. In step 3 1506, transceiver 2 (which, without loss of generality, may be referred to as the far-end transceiver) detects power. Transceiver 2 is able to distinguish the detected power from that caused by the near-end transceiver through appropriate processing of the received signal, and therefore initiates step 4 1508, which is a transmitter fast scan. Light from the signal generated in step 4 1508 by transceiver 2's fast scan reaches transceiver 1, which triggers step 5 1510, where the transceiver 1 receiver detects channel power. In various embodiments, the receiver in transceiver 1 is able to distinguish the detected channel power from that caused by the light generated in step 4 1508 by transceiver 2's fast scan. The system then moves to state 6 1512 where the transceiver remains on the current channel. Client data traffic may flow on the link.

[0170] It should be understood that the steps of the protocol for connecting a near-end transmitter to a far-end transmitter according to the present teachings can be operated in either direction, from near-end to far-end and from far-end to near-end. In addition, the various steps can be operated simultaneously or separately in time, as long as the present teachings remain operable.

[0171] One feature of the present teachings is the ability to deploy a multi-wavelength optical delivery system using multiple tunable transceivers, all with the same part number. For example, many prior art systems require transceivers with different wavelengths and / or transceiver pairs intended to be used together in a link to be tracked individually. By using network transceivers configured with hardware according to the present teachings, all the operational benefits of a single part number are realized by the service provider, including ease of deployment without tracking individual parts, reduced on-hand inventory, and remote configuration of wavelengths without prior knowledge of how the device is hardwired. For example, a technician does not manually set the wavelength of a wavelength-tunable transceiver, nor does the technician need to select an appropriate fixed-wavelength transceiver. The technician can place the hardware-configurable transceiver into any host port and connect a duplex patch cord to any fiber port on the WDM MUX / DEMUX (WDM multiplexer / demultiplexer). This eliminates the need to track the fiber from the WDM MUX / DEMUX to the transceiver. The client can then poll the transceiver's channels and create a connection map based on the channels already set in the link. In some embodiments, the remote transceiver can be located up to 2 km from the fiber optic distribution cabinet.

[0172] Figure 16 Graph 1600 shows a measured optical signal for an embodiment of a method for configuring an optical link using a transceiver configured with hardware according to the present teachings. Graph 1600 includes an oscilloscope trace 1602 of the optical output of a coherent transceiver as it traverses channels 30, 31, 32, 33, and 34, as a function of time. Graph 1600 also includes an oscilloscope trace 1604 of the output of an optical demultiplexer passing channel 32, which shows light appearing when the coherent transceiver is tuned to channel 32. Graph 1600 also includes an oscilloscope trace 1606 of a loss of signal (LOS) indicator, which shows that when a signal that has successfully passed through the demultiplexer appears at the receiver, the LOS goes low (LOS=0) because the transmitter has tuned to channel 32.

[0173] Figure 17A A top view of a transceiver representing a hardware configuration of the present teachings. Figure 17B express Figure 17BBottom view of a transceiver with a hardware configuration. The transceiver with a hardware configuration of the present teachings can be made into various packages including SFP, SFP+, or XFP specifications. Alternatively or in addition, the transceiver with a hardware configuration of the present teachings can be a CFP2 / CFP4, or a coherent transceiver. Figure 17C A top view of another embodiment of a transceiver according to a hardware configuration of the present teachings is shown. Specifically, Figure 17C A top view of a transceiver 1780 in a CFP4 specification hardware configuration is shown. In some embodiments, the hardware-configured transceiver is electronically tuned to one of 88 different wavelengths. In various embodiments, various numbers of channels are included in the system, including 88 channels, 96 channels, 16 channels, four channels, and various other channel counts. These channel wavelengths can represent specific channels on the ITU grid. In some embodiments, a link distance of up to 80 km can be achieved using a transceiver in the hardware configuration of the present teachings. In addition, in some embodiments, the operating temperature range is -5°C to 85°C. In some embodiments, the operating temperature range includes a lower range of -40°C or lower.

[0174] Figure 18 Schematic diagram 1800 illustrates an embodiment of optoelectronic components in a transceiver of a hardware configuration according to the present teachings. A tunable laser 1802, a semiconductor optical amplifier 1804, and a Mach-Zehnder modulator 1806 are positioned on a monolithic substrate 1808. Tunable laser 1802 may comprise a narrow-linewidth laser suitable for coherent transmission using a coherent modulation format. Mach-Zehnder modulator 1806 may be an InP Mach-Zehnder modulator. Mach-Zehnder modulator 1806 may be a silicon photonic modulator, also known as a SiP modulator. Mach-Zehnder modulator 1806 may comprise a low-power, compactly integrated InP IQ modulator for coherent transmission. The output of Mach-Zehnder modulator 1806 is coupled to an optical element 1810, which includes collimating optics and an optical isolator. The optical element is coupled to a power monitor and wavelength locker element 1812. These components are all placed on a thermoelectric cooler 1814. The power monitor and wavelength locker component 1812 can be configured to support tunable coherent transmit operation of the transceiver from the hardware configuration. The power monitor and wavelength locker component 1812 is coupled to a lens 1816, which is attached to a receiver 1818.

[0175] A feature of the hardware-configured optical components of this teaching is that large networks can be quickly self-configured without any intervention from host equipment or network management systems. The hardware-configured components can act autonomously and can configure themselves based on predetermined information stored in a memory device resident in the hardware-configured components. The firmware routines for configuration are self-contained in the network elements. In various embodiments, the routines enable the use of two optical fibers to configure duplex, or to configure a bidirectional single fiber connection, or both. In some embodiments, the firmware routines are initiated when the device is powered on.

[0176] Figure 19A A schematic diagram illustrates an embodiment of a WDM delivery system 1900 including transceivers configured with hardware according to the present teachings. Each of the twenty hardware-configured transceivers 1902 at the near end is connected to a WDM multiplexer / demultiplexer 1904 using two optical fibers 1906 and 1908, one for each direction. The output of multiplexer 1904 is connected to one end of an optical fiber 1910. The length of optical fiber 1910 can vary. In some embodiments, optical fiber 1910 is 80 km long, or longer. In some embodiments, optical fiber 1910 is approximately 18 km long, or longer. In some embodiments, optical fiber 1910 is less than 18 km long. The other end of optical fiber 1910 is connected to the input of a WDM multiplexer / demultiplexer 1912 at the far end. The output of WDM multiplexer / demultiplexer 1912 is connected to the twenty hardware-configured transceivers 1914 at the far end using two optical fibers 1916 and 1918, one for each direction. As used herein, the term WDM transport optical interconnect refers to a connection between a transceiver at the near end and a transceiver at the far end of an optical link configured according to the hardware of the present teachings. The WDM transport optical interconnect extends from the input of the near-end WDM multiplexer / demultiplexer 1904 to the output of the far-end WDM multiplexer / demultiplexer 1912. The WDM transport optical interconnect can include various optical components, including optical amplifiers and performance monitoring devices. Various embodiments of the WDM transport system 1900 use various types of optical transceivers 1902, 1904. Some embodiments use CFP2-compliant coherent transceivers. Some embodiments use T-SFP+ transceivers. Some embodiments use a hybrid type of transceiver.

[0177] In some embodiments, at least some of the optical fibers 1906, 1908, 1916, 1918 are approximately 2 km long, a configuration also referred to as a "remote PHY" configuration. Remote PHY is an emerging industry specification that is applied to cable head-end applications, but also to wireless and wired communication applications, including Wi-Fi, LTE, various types of passive optical networks (PONs), and other telecommunications fiber optic network applications. Remote PHY refers to an architecture that moves the physical layer transceiver element (also referred to as PHY) out of a traditional access point to place it closer to the network endpoint or end user. For example, one or more optical transceivers multiplexed in an optical WDM network can be placed away from a cable access point containing multiplexing, line conditioning, and other network element devices. For example, the optical transceiver can be placed at an enterprise. Although the examples presented here relate to the application of the present teachings in a remote PHY architecture, those skilled in the art understand that various known network architectures and industry specifications can be implemented using embodiments of the network devices and methods of the hardware configuration described herein. Furthermore, hardware-configured transceivers and / or other hardware-configured network elements of the present teachings may be located together with or remote from optical multiplexing and / or optical line conditioning and / or performance monitoring devices as part of a network.

[0178] Figure 19B express Figure 19A A schematic diagram of a WDN delivery system 1900 in accordance with an embodiment of a hardware configuration setup protocol according to the present teachings is provided. The transmitter of a near-end transceiver 1920 slowly scans wavelengths, which may be ITU wavelength channels. The slow scan duration may be approximately one second per channel. The slow scan duration is set to provide sufficient time for a receiver at a far-end transceiver 1922 to detect the light and determine that it has entered link-up. The receiver at the far-end transceiver 1922 will only receive light with wavelengths suitable for the channel to pass through the WDM multiplexer / demultiplexer 1904 1912. For example, if transceiver 1920 is connected to a WDM multiplexer / demultiplexer 1904 port for ITU 20 and is transmitting channel ITU 18, the light will be blocked 1924 at the WDM multiplexer / demultiplexer 1904. The far-end transceiver 1924 , which is expected to receive light from the near-end transmitter 1920 , is connected to the ITU 20 port of the WDM multiplexer / demultiplexer 1812 .

[0179] Figure 19C express Figure 19A 1900 is a schematic diagram of a WDN delivery system in another state of an embodiment of a setup protocol according to a hardware configuration of the present teachings. Figure 19CThe near-end transceiver 1920, which represents slow tuning, is tuned to channel ITU 20. This means that light from the near-end transceiver 1920 passes through WDM multiplexers / demultiplexers 1904 and 1912 and is delivered to the far-end transceiver 1924. Therefore, when the wavelength of the near-end transceiver 1920 matches the port of the WDM multiplexer / demultiplexer 1904, the wavelength travels all the way through the network to the far-end transceiver 1924. Consequently, the far-end transceiver 1924 detects a portion of the first optical signal sent by transceiver 1920 over the link, which has a duration equal to the dwell time of the particular channel being slowly scanned. Once the far-end transceiver determines that it is receiving light above a certain power threshold, it initiates a fast tuning optical power sequence from the transmitter at the far-end transceiver 1924. In some embodiments, the power threshold is a loss-of-signal receive power value. In some embodiments, the fast tuning optical power sequence is a step-by-step increase per wavelength channel, with a dwell time of 10 ms on each channel.

[0180] Figure 19D express Figure 19A A schematic diagram of a WDN delivery system 1900 in another state of an embodiment of a hardware configuration setup protocol according to the present teachings. The transmitter of remote transceiver 1924 can generate a rapid scan of wavelengths. The transmitter of remote transceiver 1924 rapidly scans a sequence of wavelengths, which can be wavelengths of ITU wavelength channels. The dwell time on any one channel during the scan is referred to as the rapid scan duration. In some embodiments, the rapid scan duration is approximately 10 milliseconds per channel. Figure 19D The snapshot shows that the transmitter is generating illumination under channel ITU 18, which will not pass through the port that passes channel ITU 44.

[0181] Figure 19E express Figure 19A A schematic diagram of a WDN delivery system in another state of an embodiment of the hardware configuration setup protocol of the present teachings is shown. The fast-tuning transmitter in far-end transceiver 1924 hits channel ITU 44, which is passed through the ports of WDM 1912 and WDM 1904 to be received at the receiver of near-end transceiver 1920. Consequently, the wavelength of the far-end transmitter matches the wavelengths used for both ports, and the light travels through the network to near-end transceiver 1920. Consequently, near-end transceiver 1920 detects an optical pulse with a duration equal to or less than the dwell time on the specific wavelength channel during the fast scan. At this point, both transceivers 1920 and 1924 can lock onto their transmit wavelengths and begin normal operation, including delivering real-time client traffic. In other words, the transceivers maintain their respective transmitters at their current operating wavelengths, completing the bidirectional link and initiating communication.

[0182] Each of the twenty hardware configured transceivers 1902 connected to the proximal end of the twenty hardware configured transceivers 1914 by a WDM interconnect comprising optical multiplexers 1904, 1912 and optical fiber 1910 can be configured using various embodiments of the methods of the present teachings. For example, the transceiver pairs can be configured using a combination of Figure 12A -B describes two unidirectional protocols to be configured, or a transceiver pair can be combined by using Figure 14 In some embodiments, the WDM interconnect may be configured using a single bidirectional protocol as described above. Alternatively, some transceivers may be configured using a lookup table containing data regarding which wavelength channels the WDM interconnect will pass in each direction between a particular pair of transceivers. In embodiments using a lookup table, the wavelength is tuned directly to the predetermined channel, and a connection is immediately established between the transceivers at the near and far ends of the link. This use of a lookup table for establishing an operating wavelength for transmitting real-time traffic between transceivers will speed up the connection time used to configure the link. The use of a lookup table may be performed for any or all of the unidirectional and / or bidirectional link configurations in a multi-transceiver WDM system. For example, in some embodiments, a lookup table may be available with data regarding some, but not all, of the wavelength channels that are passed through the WDM interconnect connection between a particular near-end / far-end transceiver pair.

[0183] A feature of the present teachings is that the links of optical elements used in the hardware configuration can be amplified links. In some embodiments with high-loss and / or long-distance fiber links, optical gain and / or compensation for fiber dispersion (including chromatic dispersion) may be required. In addition, control, monitoring, and troubleshooting of WDM networks may be desirable for one or all channels. Figure 20 Figure 2000 illustrates an embodiment of a remote PHY subsystem 2000 with the gain of the present teachings. Package 2002 supports two remote PHY links in a 1RU. Package 2002 supports optical gain, a compact, high-resolution optical channel monitor (OCM), and can provide performance monitoring at each wavelength. In some embodiments, remote PHY subsystem 2000 can support fiber transport links up to 60 km.

[0184] Figure 21A schematic diagram of a WDN delivery system with gain utilizing elements of the hardware configuration of the present teachings. The elements of the hardware configuration can be configured in a remote PHY configuration. Remote PHY systems typically separate the transceiver device from the multiplexing and link technology via relatively long fiber links, as opposed to housing them in the same box. This allows the transceivers to be deployed in locations far from the multiplexing and link technology. Twenty transceivers 2102 in the near-end hardware configuration are connected to a WDM multiplexer / demultiplexer 2106, which is remotely connected to the transceivers 2102 using two optical fibers 2108 and 2110 (one in each direction) for each transceiver 2102. The optical fibers 2108 and 2110 are typically 2 kilometers long, but in some systems can be longer. The output of the WDM multiplexer / demultiplexer 2106 is connected to a first WDM 2112. The output of the first WDM 2112 is connected to an optical amplifier 2114. The output of optical amplifier 2114 is connected to a second WDM 2118. One output of second WDM 2118 is connected to a second optical amplifier 2120, which is connected back to first WDM 2112. Another output of second WDM 2118 is connected to a splitter, which sends some light to a high-resolution optical channel monitor 2124. The high-resolution optical channel monitor controls both optical amplifiers 2114 and 2120 to maintain a high-quality optical signal on each wavelength channel. A second output of the splitter is connected to a delivery fiber 2126. In some embodiments, delivery fiber 2126 is approximately 58 km long, but in other embodiments, it can be longer. The other end of delivery fiber 2126 is connected to the input of a remote WDM multiplexer / demultiplexer 2128. The output of WDM multiplexer / demultiplexer 2128 is connected to twenty hardware-configured transceivers 2130 at the remote end using two optical fibers 2132 and 2134 (one fiber for each direction). In some embodiments, at least some of the optical fibers 2132, 2134 are approximately 2 km long, but in other embodiments may be longer.

[0185] Another feature of the present teachings is that they can be configured for different network applications. For example, the network elements of the hardware configuration of the present teachings can be configured for a typical telecommunications service provider network configuration. Alternatively, the network elements of the hardware configuration of the present teachings can be configured for a typical data communication service provider network configuration.

[0186] Figure 22A An embodiment of a remote PHY system 2200 is shown of a network element using a hardware configuration of the present teachings configured for telecommunications applications. Figure 22B

[00106] An embodiment of a remote PHY system 2250 is shown of a network element using a hardware configuration of the present teachings configured for data communications applications. In some embodiments, the remote PHY system 2200, 2250 includes front-to-back cooling. In some embodiments, the remote PHY system 2200, 2250 has dual redundant hot-swappable power supplies accessible from a rear panel. The power supplies can be either AC or DC. In some embodiments, the remote PHY system 2200, 2250 includes dual redundant hot-swappable fan units accessible from a rear panel. In some embodiments, the remote PHY system 2200, 2250 has a 1U form factor with a depth of 450 mm. In some embodiments, the remote PHY system 2200, 2250 includes a front panel that is devoid of optical connectors and is capable of supporting approximately one hundred LC type connectors.

[0187] Figure 23A An embodiment of a front panel 2300 of a remote PHY system for a network element using the hardware configuration of the present teachings is shown. The remote PHY system can support two remote PHYs. Front panel 2300 includes primary and secondary line ports 2302. The secondary line port is optional. A monitor port 2304 is included. The first remote PHY includes forty multiplexer / demultiplexer ports 2306. In addition, there are forty multiplexer / demultiplexer ports 2308 for the second remote PHY.

[0188] Figure 23B An embodiment of a rear panel 2350 of a remote PHY system of a network element using the hardware configuration of the present teachings is shown. There are dual redundant hot-swappable fan units 2352, 2354. Each fan unit includes two fans. There are dual redundant hot-swappable power supplies 2356, 2358.

[0189] Figure 24 A schematic diagram showing the functional blocks and layout of an embodiment of a remote PHY system that supports two remote PHYs of a network element configured using the hardware of the present teachings. A multiplexer / demultiplexer port 2402 on the front panel supports a first and a second remote PHY connection. The remote PHY system includes fan units 2404, 2406 and two power supplies 2408, 2410. There are two dual optical amplifiers 2412, 2414, which may be erbium doped fiber amplifiers (EDFAs). There is also an optical performance monitor 2416. There are also two groups of dispersion compensation units 2318, 2320, each group of two dispersion compensation units. There is an optical switch 2422 and a fiber management system 2424. There are also two WDM multiplexers / demultiplexers 2426, 2428. Thus, this embodiment of the remote PHY system is capable of supporting a network element that may be configured to combine Figure 21 Some of the elements of the hardware configuration of the two WDM transport systems of the remote PHY system are described.

[0190] The optical channel monitor measures the number of wavelengths, the optical power level of each channel, and the OSNR of each channel. Automatic setup and configuration of the optical channel line monitor for primary and secondary links is supported. The optical output power is optimized for the best bit error rate (BER) for each receiver. The power can be set to + / - 2dB for each receiver. This is critical for links with low OSNR. Dynamic system optimization can be performed, in which the optical performance monitor provides real-time feedback to adjust optical amplifier and variable optical attenuator settings for balancing power in each channel.

[0191] A feature of the methods and apparatus of the present teachings is that no manual entry of parameters is required, which reduces setup time and minimizes errors. There is also no need to pre-measure parameters on the fiber link (such as distance, link loss, etc.). Link loss versus distance can vary greatly depending on fiber quality, connection loss, and changes in passive optical components. Previous systems required measurement of each link and also suffered from this because errors in manually entering connections may not be discovered until a fiber is cut or other service is disrupted. This means that service is disrupted. The optical performance monitor of the present teachings provides early warning of OSNR or power degradation of each wavelength channel, which means that scheduled maintenance can be performed before the link goes down. This improves service quality and reduces customer downtime. The optical performance monitor of the present teachings also helps to find the source of link problems, whether they are in the multiplexer / demultiplexer or in the remote PHY transceiver. The improved operational properties of the network configured with the hardware of the present teachings reduce service truck rolls and reduce the time and cost of running the network.

[0192] One feature of the hardware configurable transceivers of the present teachings is that they simplify the deployment of systems that utilize wavelength tunable optical transceivers. For example, various dense wavelength division multiplexing (DWDM) transceivers used in remote PHY access networks are built by multiple system operators (MSOs). These systems can include products such as the Finisar Corporation Flextune and the Optical amplifiers, and 200G coherent optical transceivers supporting commercial services.

[0193] Some embodiments of WDM delivery systems utilizing hardware-configured transceivers of the present teachings enable up to ninety-six wavelength-tunable optical transceivers in a remote PHY network to self-configure their wavelengths to operate on a DWDM infrastructure without input from host equipment or intervention from a technician. The technician plugs the hardware-configured transceiver into any host port in the headend equipment and remote PHY nodes and connects the hardware-configured transceiver to any of the optical multiplexer ports using fiber optic patch cables. The firmware and controller contained in the transceiver determine the appropriate wavelength to link the headend equipment to each remote PHY node.

[0194] Rather than having to stock many different fixed-wavelength modules, operators only need to stock one universal, hardware-configured, wavelength-tunable transceiver according to the present teachings. Configuration time for a transceiver link using a fixed-wavelength module might take hours. Configuration time for a link using a hardware-configured transceiver might take minutes or less. Furthermore, technicians do not have to trace optical fibers from the optical multiplexer to the remote PHY nodes. These fibers can be 2 km or longer.

[0195] Some embodiments of the transceiver of the hardware configuration of the present teaching utilize Finisar's 10Gb / s wavelength tunable duplex and dual-band bidirectional (BiDi) transceivers. In these embodiments, the dual-band BiDi SFP+ transceiver adapts a pair of wavelengths to each port of a standard 100GHz DWDM multiplexer and demultiplexer. This enables up to eighty wavelengths to be deployed on an existing forty-wavelength DWDM network. This results in an increase in data capacity from 200Gb / s to 400Gb / s in each direction on a single optical fiber without replacing the entire infrastructure. Because it has only one optical connection for a pair of wavelengths, the BiDi transceiver also reduces the number of fiber optic patch cables by a factor of two, which simplifies installation and saves space.

[0196] A feature of this teaching is to support the method for automatically discovering or configuring the link of the optical component including hardware configuration. This automatic discovery function is also referred to as establishing a link, establishing a connection, connecting a link, starting a connection and similar terms in the art. Automatic discovery can be carried out without any intervention from a human operator, and / or once the component is wired into the link, without using an external network management system. The various steps of the discovery method according to this teaching can be referred to as a connection protocol, a connection algorithm and / or a discovery protocol or algorithm. An embodiment of the method according to this teaching generally relates to one or more of the steps for pre-configuring a module, powering on a module and tuning the module operating wavelength. The method can be used, for example, to turn on and off radio frequency (RF) modulation (the RF modulation can, for example, include customer data traffic in a transceiver module), and is also used to complete other steps involved in establishing an optical link.

[0197] It should be understood that although the purpose of various embodiments of the method according to the present teachings is to establish a communication link between two hardware-configured elements, the various steps of the method can be implemented in whole or in part to achieve other purposes, such as testing, network reconfiguration, and various other operations. The communication link can be unidirectional and / or bidirectional. The hardware modules involved in the method for discovering hardware-configured links can be, for example, optical transceiver modules. Some embodiments of the hardware modules can include other elements in the link, such as amplifiers, wavelength selective switches, and many other devices. The method is effectively applied to the discovery of new links and to the addition of devices to existing links that include operational connections that are not established by embodiments of the method of the present teachings.

[0198] A feature of the method of the present teachings is that it enables deployment on existing systems because it uses a transparent connection of an optical control plane that operates independently of the customer data traffic control plane. That is, there is no need to demodulate the customer data to configure the elements. The optical control plane refers to the connections and protocols that the hardware configured elements use to implement management purposes (such as link discovery). The optical control plane, in some embodiments, operates only between optical transceivers and / or other hardware configured optical elements in a link and does not necessarily need to be connected to a host management system, or to other elements in the optical system, for configuration. The hardware configured elements do not need to be connected to or integrated into an existing physical layer control plane or data plane control system to become operational.

[0199] The optical control plane of the present teachings is used to automatically discover links, for example, after powering up the transceiver, without interacting with any operational control system for existing traffic. This is because the hardware-configured transceiver can be configured to sense other operational traffic during the discovery process without interrupting that traffic. In this way, a fiber optic cable plant that is carrying real-time traffic can be upgraded, for example, from a direct detection link operating at a rate of 100 Gb / s or less to a coherent link operating at a rate of 400 Gb / s or more. A feature of the optical control plane of the present teachings is that there will be no service disruption during the upgrade because the operational traffic does not need to be taken offline.

[0200] A feature of the method and apparatus of the present teachings is the ability to automatically discover optical links using coherent optical signaling formats using hardware-configured SFP+ transceivers. The control information is modulated at a rate lower than the data rate of the traffic. Another feature of the method and apparatus of the present teachings is that it can be used to automatically discover optical links that do not have flexible or tunable optical multiplexers (such as WSS) to combine signals onto the transport fiber. The link can be unidirectional or bidirectional. In addition, the link can use a transceiver configured for direct detection or coherent signaling formats, or a combination of these formats. The transceiver can also be either a tunable transceiver or a fixed transceiver.

[0201] Another feature of the method and apparatus of this teaching is that it can be used to automatically configure optical links with various multiplexing and demultiplexing capabilities. Multiplexer and demultiplexer devices are commonly referred to as combiners and / or splitters. The terms splitter and combiner can be used interchangeably when referring to these devices. Splitter and combiner combine and separate optical signals from one or more inputs to one or more outputs and can operate in two directions as is well known to those skilled in the art.

[0202] As an example of various multiplexer / demultiplexer capabilities, the present teachings are that some embodiments of coherent links use passive splitters / combiners without any wavelength filtering. Some link embodiments use fixed filter splitters, such as arrayed waveguide grating (AWG) devices. Other embodiments use flexible, tunable filter splitters, such as wavelength selective switches (WSS). Embodiments using filter splitters and combiners can use direct detection, coherent detection, or a combination of these two transceiver types. Some link embodiments use a bidirectional single fiber link. Other link embodiments use two unidirectional optical fibers to form a bidirectional link.

[0203] Some embodiments use a coherent architecture with a single laser within the transceiver, in which the receive operating wavelength is the same as the transmit operating wavelength. This is because the transmit and receive operations share the same local oscillator (LO) laser device. In these embodiments, a bidirectional link operates on the same wavelength for both directions. This architecture therefore does not allow receiving on one wavelength and transmitting on another wavelength because the transmit and receive paths share the same laser.

[0204] In some embodiments of systems according to the present teachings, an AWG and / or WDM demultiplexer is not present, resulting in an optical link where both ends operate on the same ITU channel. Furthermore, in some embodiments of systems according to the present teachings, transmission occurs on separate wavelengths. In these embodiments, the receive path operates in listening mode to determine the desired broadcast ITU channel. In these embodiments, there is no downlink, only an uplink. In other words, a unidirectional link is established.

[0205] In embodiments of systems according to the present teachings in which at least some of the transceivers use direct detection, the receivers are not operational. For direct detection systems, the transceivers do not use a coherent signal format. This means that these receivers do not require a local oscillator laser to function. Therefore, one wavelength can be received via a WDM demultiplexer or WSS and transmitted on a different laser wavelength.

[0206] A feature of the present teachings is that coherent transceivers can be used for some channels of a WDM system that are provided by transceivers that utilize direct detection. That is, coherent transceivers can be added to an existing system that uses direct detection for some channels.

[0207] Some embodiments of the present teachings use fixed, wavelength-filtering combiners / splitters. Figure 25A schematic diagram illustrates an embodiment of a WDM transport link 2500 according to the present teachings, which utilizes two unidirectional optical fibers 2502, 2504 to connect hardware-configured tunable transceivers, transceiver 1 2506 and transceiver 2 2508, using fixed, non-tunable AWG filters 2510, 2512, 2514, 2516. The transmitter of transceiver 1 2506 is connected to the input port of AWG 2510 to transmit an optical signal to AWG 2512 via optical fiber 2502. The signal from the transmitter of transceiver 1 2506 is passed to the output port of AWG 2512, which is connected to the receiver of transceiver 2 2508. The transmitter of transceiver 2 2508 is connected to the input port of AWG 2516 to transmit an optical signal to AWG 2514 via optical fiber 2504. The signal from the transmitter of transceiver 2 2508 passes to the output port of the AWG 2514 which is connected to the receiver of transceiver 1 2506 .

[0208] The discovery method of automatically establishing a link according to the present teachings eliminates upper layer software and connects the link after the transceivers 2506, 2508 on both sides of the link 2500 are powered on. Figure 25-27C For purposes of describing the method of the present teachings in association, channel 5 2518 is selected for the transmit side of transceiver 1 2506 and channel 5 2520 is selected for the receive side of transceiver 1 2506. These are the channels that carry the path from the transmitter at one end of the link to the receiver at the other end of the link through the AWG connection. The two ends of the link may be referred to as the near end and the far end to distinguish between the two ends without loss of generality. Figures 26A-27C An embodiment of a method of automatically establishing a link between two ends is further described.

[0209] Figure 26A express Figure 25 A state diagram of an embodiment of a method for automatic channel discovery of an optical link according to a hardware configuration. Figure 25 and Figure 26A In both figures, transceivers 2506, 2508 have a loss of signal (LOS) indicator, where LOS=1 means no light is detected and LOS=0 means light is detected in the receiver. The link system typically starts in an idle state 2602. This idle state 2602 occurs, for example, when both transceivers 2506, 2508 are powered on. One rule of the state machine shown in state diagram 2600 is that if LOS is generating a "beacon" signal, where the signal is, for example, as described above in conjunction with Figure 13-142600. The Slow Scan and Fast Scan wavelength tuning parameters are combined with the above Figure 13-14 Those parameters described are the same or similar. From the slow scan state 2604, when the receiver in transceiver 2506, 2508 detects LOS = 0 (where the power value is positive, but the duration is shorter than the duration of two consecutive fast scan pulses, as shown in received power graph 2608), the associated transmitter transitions to the TX BEACON state 2610, in which the transmitter generates a beacon signal. This LOS = 0 condition represents that a single pulse from the fast wavelength scan is being sensed by the receiver.

[0210] From state SLOW SCAN 2604, upon receiving LOS = 0 (where the duration of power is longer than the duration of two consecutive fast scan pulses, as shown in received power graph 2618), the transmitter transitions to FAST SCAN 2620, in which the transmitter provides a fast channel wavelength scan. The LOS = 0 condition indicates that the duration of light on the detector is longer than a single fast scan pulse, thus indicating that light from the other end transmitter has made it to the receiver. From fast scan state 2620, the system transitions to a second slow scan state 2622. Upon detecting BEACON = OFF, the system transitions to HOLD state 2624.

[0211] From the TX BEACON state 2610, upon receiving LOS=0 (where the pulse duration is longer than at least half the duration of the slow scan dwell time, as shown in the received power graph 2612), the transmitter transitions to the TX HOLD state 2614. In the TX HOLD state 2614, the transmitter continues to maintain the current wavelength channel to which it is tuned. From the TX HOLD state 2614, upon receiving LOS=1, as shown in the received power graph 2616, the transmitter transitions to the TX SLOWSCAN state 2604. From the TX BEACON, in the event that LOS=1 is received for a duration greater than the slow scan period, the transmitter transitions to the SLOW SCAN state 2604. The received LOS=1, as shown in the received power graph 2616, initiates a transition from the HOLD state 2624 to the SLOW SCAN state 2604.

[0212] Figure 26B express Figure 25 26. A process flow diagram of an embodiment of a method 2650 for automatic channel discovery of an optical link using a hardware configuration is provided. This flow diagram is intended to illustrate the steps involved in state transitions in an embodiment of the method 2650 of the present teachings. It should be understood that the numbering of the steps in this process flow diagram does not imply a specific order and / or timing for performing the steps of the method 2650. In various embodiments, it is contemplated that all or a portion of the steps described may be used consistent with the present teachings. Figure 26B An SFP+ type transceiver is described, but other embodiments may use other transceiver types. Figure 26B Here is the use Figure 25 However, as will be appreciated by those skilled in the art, various transceiver configurations may be employed. Figure 26B It should also be understood that multiple transceivers can operate in parallel and / or serially using the steps of method 2650 to establish multiple optical links between transceivers without human and / or management system intervention. Unidirectional and bidirectional links can also be established. In addition, although the description includes the predetermined threshold P th As well as various durations and times discussed, these represent only specific embodiments. In various embodiments, various power thresholds can be used, and the various decision steps can also use the same or different thresholds. Various durations and pulse widths can also be used as described herein.

[0213] Step 1 2652 of the method is to enable a transceiver (such as Figure 25 The description of the method is continued by discussing only one transceiver, it is understood that any number of transceivers can perform the various steps of the method in various embodiments of the method of establishing a link using the method of the present teachings.

[0214] In step 2 2654, the transmitter laser in the transceiver begins transmitting power on channel N. In step 3 2656, the transmitter laser waits one second on that channel and then changes to channel N+1 in step 4 2658. In decision step 5 2660, the receiver in the transceiver monitors the power and determines if the received power is greater than a predetermined threshold P. th In some embodiments, the threshold is an established loss of signal received power value. For example, the loss of signal received power level may be in the range of -35dBm to 0dBm, depending on the application.

[0215] The receiver also determines whether the detected power has a duration equal to a specific predetermined value. The duration is selected to be the duration of the fast scan dwell time on a specific channel. In some embodiments, the specific value of the pulse duration is 10ms. Figure 26B As described herein, the duration may also be referred to as a pulse width (PW). If the receiver does not sense a power greater than a predetermined threshold and a duration or pulse width equal to 10 ms or another predetermined value, the method proceeds to another decision in step 6 2662. In step 6 2662, the receiver continues monitoring to determine whether the duration of the received power and the duration or pulse width PW exceed 10 ms. If so, the method moves to step 7 2664, in which the transmitter initiates a fast scanning wavelength scan sequence as described herein.

[0216] In decision step 8 2666, the receiver in the transceiver monitors the power and detects the optical power. The receiver determines whether the detected optical power is greater than a predetermined threshold value P th , and whether the detected optical power has a timing pattern with a duration consistent with a beacon signal as described herein. If a beacon signal is detected, the method proceeds to step 92668, and the wavelength channel is incremented by one channel when the transmitter of the transceiver detects the beacon. In decision step 102670, the receiver in the transceiver continues to monitor the optical power and determines whether the detected optical power is greater than a predetermined threshold value P th , and whether the detected optical power has a duration greater than a certain duration of the beacon signal ON state (in this example, 0.5 seconds). If so, the method proceeds to step 11 2672, in which the transmitter in the transceiver moves to the HOLD state as described herein. In decision step 12 2674, the receiver in the transceiver monitors the power and detects the optical power. If the power is not less than a predetermined threshold P th , the system enters step 112672. That is, the system remains in the HOLD state. However, if the power drops below a predetermined threshold value P th , the method moves back to step 2 2654 to begin another slow scan as described herein.

[0217] If, in the decision associated with step 5 2660, the receiver in the transceiver monitors the power and determines that the received power is greater than a predetermined threshold value P th, and the duration is greater than the dwell time on a particular channel for the quick scan (for some embodiments, this is PW=10ms), then the method proceeds to step 13 2676 and the transmitter in the transceiver moves to the BEACON state as described herein. In decision step 14 2678, the receiver monitors the detected optical power and determines whether the detected optical power is greater than a predetermined threshold P th If not, the method returns to step 13 2676. If yes, the method proceeds to step 15 2680 and the transmitter moves to the HOLD state as described herein. In decision step 16 2682, the receiver monitors the detected optical power and determines whether the detected power is less than a predetermined threshold value P th If not, the method returns to step 15 2680. That is, the transceiver remains in HOLD. If yes, the method returns to step 2 2654 to begin another slow scan as described herein. In some embodiments, the predetermined threshold P th is the power that results in a LOS = 0 condition at a transceiver connected to the link. That is, that is the power detected at that transceiver from the optical signal being present on the link.

[0218] Figure 27A Indicates that Figure 25 An embodiment of a method for link connection associated with an optical link of a hardware configuration, a graph 2700 showing optical power as a function of time for a set of transmitter and receiver states and associated state timing diagrams. Figure 25-27A Graph 2700 shows a transmitted optical signal 2702 generated by the transmitter at near-end transceiver 1 2506 in the SLOW SCAN state 2604, a received optical signal 2704 received at the receiver at far-end transceiver 2 2508, a transmitted optical signal 2706 generated by the transmitter at far-end transceiver 2 2508, and a received optical signal 2708 received at the receiver at near-end transceiver 1 2506. Graphs of the following timing diagrams are also shown: a timing diagram 2710 for the HOLD state 2614 of the transmitter at near-end transceiver 1 2506, a timing diagram 2712 for the BEACON state 2610 of the transmitter at near-end transceiver 1 2506, and a timing diagram 2714 for the HOLD state 2614 of the transmitter at near-end transceiver 2 2508. In the timing diagrams, a high state represents the active state and a low state represents the active state.

[0219] exist Figure 27AIn the illustrative example presented in FIG, transceiver 1 2506 is turned on and begins in TX_SLOW_TUNE state 2716, thereby traversing wavelength tuning, starting with channel 1, at a rate of, for example, one second per channel. When transceiver 1 2506 is tuned to channel 5, signal 2718 is detected at transceiver 2 2508. In some embodiments, the receiver specifically detects that the duration of this signal is longer than the time it takes to traverse two channel tunings for the fast scan duration, which is twice the fast scan duration. This is evidenced by the transceiver monitor generating LOS=0 for this duration. The reason for monitoring the duration in addition to the presence or absence of light on the detector is to ensure that the detection is a slow scan and not a fast scan, which would only last for the duration of the fast scan pulse. Monitoring is optional. Signal 2718 detected at transceiver 2 2508 causes the transmitter in transceiver 2 2508 to implement TX_FAST_TUNE 2720, a fast optical wavelength scan. During this fast scan 2720, when channel 5 is transmitted from transceiver 2 2508, light passes to transceiver 1 2506 and a receive signal 2722 is detected at transceiver 1 2506 as shown at 2722. This causes transceiver 1 2506 to transition to the TX_HOLD state 2614 on channel 5 at location 2724 as shown in timing diagram 2710. As shown by the transmit signals 2730 2728 and receive signals at transceiver 2 2508 turning channel 5 on and off, transceiver 1 2506 transitions to the TX_BEACON state 2726 on the same channel 5. The detection of this beacon signal causes the transmitter in transceiver 2 2508 to begin the TX_SLOW_TUNE state 2604 as shown at time 2732. The receiver in transceiver 1 2506 detects the optical signal transmitted from transceiver 2 2508 while it is tuned to channel 5, so a detection signal 2734 is generated. This detection of the signal in transceiver 1 2505 causes transceiver 1 2505 to move from BEACON to HOLD at positions 2736 and 2738 as shown in the timing diagram. Detecting the transition from BEACON to HOLD then causes transceiver 2 2508 to remain on channel 5 2740 (the current wavelength channel in this example). A bidirectional link is now established, and traffic can flow in both directions.

[0220] Figure 27B An experimental setup 2750 showing an embodiment of a method for link connection associated with an optical link of a hardware configuration of the present teachings for measuring optical power as a function of time. Two transceivers 2752, 2754 are connected in a unidirectional manner via two optical fiber links 2764, 2766 through AWGs 2756, 2758, 2760, 2762.

[0221] Figure 27C Indicates that Figure 27B An oscilloscope trace 2780 showing optical power as a function of time in accordance with an embodiment of a method for configuring a connection protocol associated with an optical link in accordance with a hardware configuration. Figure 27B In Figures 2-C, there is a trace 2782 associated with a first transceiver 2752 and a trace 2784 associated with a second transceiver 2754. The first transceiver 2752 is shown running a slow scan 2786 and a beacon 2788. The second transceiver 2754 is shown running a fast scan 2790. For a 40 wavelength channel system, the slow scan requires 40 seconds to scan all channels. However, as will be appreciated by those skilled in the art, various other scan times are possible in various embodiments of the slow wavelength scan of the present teachings.

[0222] A feature of the present teachings is that the connection protocol method can be applied to transceivers using a coherent signaling format. Coherent transceivers contain a tunable transmitter and a tunable receiver. The wavelength is based on the laser channel set point. A photodiode in the receiver allows the total power to be monitored, which is equivalent to a non-coherent SFP+ tunable transceiver. This allows for simple connection without the need for labeling or fiber numbering.

[0223] Figure 28A A schematic diagram illustrates an embodiment of a WDM transport link 2800 according to the present teachings. The WDM transport link 2800 utilizes two unidirectional optical fibers 2802 and 2804 to connect hardware-configured tunable coherent transceivers, transceiver 1 2806 and transceiver 2 2808, using filter-based combiners / splitters 2810, 2812, 2814, and 2816. In some embodiments, combiners / splitters 2810, 2812, 2814, and 2816 are AWG filters. In some embodiments, combiners / splitters 2810, 2812, 2814, and 2816 are WSS devices. The transmitter of transceiver 1 2806 is connected to the input port of combiner / splitter 2810 to transmit an optical signal to combiner 2812 via optical fiber 2802. The signal from the transmitter of transceiver 1 2806 is passed to the output port of combiner / splitter 2812 connected to the receiver of transceiver 2 2808. The transmitter of transceiver 2 2808 is connected to the input port of combiner / splitter 2816 to send the optical signal to combiner / splitter 2814 through optical fiber 2804. The signal from the transmitter of transceiver 2 2808 is passed to the output port of combiner / splitter 2814 connected to the receiver of transceiver 1 2806. The connection protocol method and the combination for link 2800 are shown in FIG. Figure 25 Link 2500 described, and also in conjunction with Figures 26A-27CThe connection protocol methods described can be the same.

[0224] Figure 28B express Figure 28A State diagram 2820 of an embodiment of a method for automatic channel discovery of an optical link in a hardware configuration. Generally speaking, for a coherent system using a filter combiner splitter (such as an AWG), embodiments of the method utilize a method that combines Figure 25-27C The situation is similar to that described for the SFP+ case. It is necessary that the wavelength from the transmitter can pass through the filters connecting the transceiver pair and be compatible with the receiver on the other side. The tuned wavelength is generated by a tunable local oscillator laser in the transceiver. As described earlier, the transceiver has a loss of signal (LOS) indicator, where LOS = 1 means no light is detected and LOS = 0 means light is detected in the receiver.

[0225] The optical link may be in an idle state 2822. This idle state 2822 may exist, for example, at system startup and / or transceiver power-up. The system has an allowable transition from the idle state 2822 to a slow scan state 2824. The slow scan state 2824 is also referred to as SLOW_SCAN_T, in which the transmitter tunes its wavelength by scanning channels at a slow rate. This transition may be automatically triggered, for example, at some time after startup. Each channel change in the scan associated with the slow scan state 2824 is shown as a channel change transition 2826 in the state diagram 2820. The slow scan and fast scan wavelength tuning parameters are combined with the above Figure 13-14 The parameters described are the same or similar. From the slow scan state 2824, when the receiver in the transceiver detects LOS = 0 (where the power value is positive and lasts longer than the duration of two consecutive fast scan pulses, as shown in the received power graph 2828), the associated transmitter transitions to the TX OFF, LO_FAST_SCAN state 2830. In the TX OFF, LO_FAST_SCAN state 2830, the transmitter is first shut down, for example, by using the VOA with the SOA set to off, thereby preventing the optical signal from leaving the transmitter. Furthermore, the transceiver receive local oscillator generates a fast scan of the wavelength channels with the transmitter modulation turned off, thereby generating a short pulse of light of a predetermined duration for each of the sequence of wavelength channels as described herein. The receiver thus obtains a signal when the specific channel being transmitted matches the receive LO channel. In this way, the transceiver determines the channel number of the received light. Therefore, there is no need to track the specific channel associated with the wiring of the filtering AWG, as it is discovered autonomously by the transceiver elements.

[0226] Transitioning out of the Slow Scan state 2824 is also triggered by the receiver detecting LOS = FAST_SCAN_LO_T. That is, LOS = 0 or power is detected for a brief duration of the fast scan pulse time. Under this condition, the transceiver state transitions to the HOLD state 2836. For more than two fast scan pulse durations, the HOLD state 2836 remains at LOS = 1 or no power is detected, and transitions to the Slow Scan state 2824.

[0227] From the TX OFF, LO_FAST_SCAN state 2830 on the detection channel for receiving direct detection, the transmitter is set to the detection channel and enters the Generate TX Short Pulse state 2834. This state effectively generates an "ACK" to the far side, indicating that light was detected, the channel is determined, and the transceiver is ready for the HOLD state for another transceiver. The TX Short Pulse state 2834 then transitions to the HOLD state 2836.

[0228] Figure 28C express Figure 28A 28. The process flow diagram of an embodiment of a method 2850 for automatic channel discovery of an optical link for a hardware configuration of FIG. 28. For the optical link setup, the transceivers on both sides are powered on. The first step 2852 is to power on the transceiver. In step 2854, the transceiver begins a slow tuning of the wavelength, starting from wavelength channel N. In step 3 2856, the laser is held on the wavelength channel from step 2 2854 for 1 second. As described herein, in some embodiments, other predetermined long scan channel durations are used instead of the 1 second duration. Then, in step 4 2858, the channel is changed to N+1. In step 5 2860, it is determined whether the received power in the transmitter has exceeded the threshold value P. th If not, the method moves back to step 2 2854 and the slowly tuned channel is incremented. If the received power in the transmitter has exceeded the threshold P th, the method moves to step 6 2862 and the transmitter is turned off. In some embodiments, transmitter shutdown is achieved via VOA, but other known shutdown methods such as SOA may be used. In step 7 2864, the transceiver performs a fast tune of the receiver LO to find the value of the wavelength channel being transmitted. In step 8 2866, the transmitter in the transceiver is set to the channel found by the LO receiver fast tune, and in step 9 2868, a short pulse is sent as an "ACK" to acknowledge receipt of the signal and initiate HOLD in the other transceivers. Decision step 10 2870 determines if the received power exceeds a threshold, and if so, in step 11, a transmitter HOLD state 2872 is initiated. Decision step 12 2874 effectively holds the state until power is lost. If the received power drops below P th , the method proceeds to step 2 2854. Otherwise, it proceeds to the HOLD state at step 11 2872. In decision step 10 2870, if the received power is not greater than the predetermined threshold, the method moves to step 2 2854 to perform slow tuning of the wavelength.

[0229] A feature of the present teachings is that embodiments using coherent transceivers do not require a rapidly scanned signal to be sent across the link. A rapidly scanned optical signal is generated in the transceiver and then mixed with an incoming signal to the transceiver. When the incoming signal has the same wavelength channel as the rapidly scanned wavelength channel, a short pulse of light with a dwell time nominally equal to the dwell time of the specific channel in the rapid scan is detected at the output of the mixer in the transceiver. This detection of an optical pulse with a duration equal to or less than the dwell time on the specific wavelength channel in the rapid scan provides information for proceeding with link establishment as described herein.

[0230] Figure 28D Indicates that Figure 28A Graph 2880 shows optical power as a function of time, showing a set of transmitter and receiver states present during an embodiment of a method for automatic channel discovery of an optical link in a hardware configuration. Trace 2882 of the transmitter in transceiver 1 2806 represents transceiver power-up and the start of a slow scan. Trace 2884 of the receiver direct detection in transceiver 2 2808 represents the power detected from transceiver 1 2806 via direct detection, without mixing with the local oscillator in transceiver 2 2808. This indicates that it is channel 5, which has passed through combiners / splitters 2810, 2812, 2814, and 2816. Trace 2866 of the transmitter output in transceiver 2 2808 and trace 2888 of the receive LO laser in transceiver 2 2808 show the power being detected by the receiver directly from transceiver 1 2806. Figure 28BThe start of the slow scan is interrupted by a state transition to the TX OFF, LO_FAST_SCAN state 2830. As indicated by trace 2890 of the mixed signal detected in transceiver 2 2808, channel 5, the mixing of the incoming signal with the sweep of the local oscillator generates a confirmation that the received signal is channel 5. At this point, transceiver 2 2808 generates a short pulse "ACK" (see trace 2886). Receipt of the "ACK" is indicated by trace 2893 of the receiver signal in transceiver 1 2806. As indicated by traces 2894 and 2896, both transceiver transmitters initiate a HOLD on channel 5. The optical link is established, and client data traffic can be sent over the link.

[0231] The link configurations taught herein are used in a variety of different use cases, including, for example, data centers, cable television distribution, and / or telecommunications applications. For example, there are currently numerous deployments in data centers using 1.6-terabit switches built with individual 100-Gb / s transceivers. These data center deployments are trending toward 400-Gb / s data communication optical pluggable transceivers using coherent optical signaling. With 100-Gb / s coherent signaling, in some configurations, there is a 30dB dynamic range. For 400-Gb / s in some configurations, there is a 22dB dynamic range. In configurations with longer links, EDFAs are used. This large dynamic range enables the use of up to 1×16 passive, non-filtering splitters at both ends of the link. In amplified links, larger passive splitters, such as 1×64, can be used. This passive, non-filtering splitter configuration can support bidirectional traffic without amplifiers. The absence of filters in the link means that unlabeled connectors to the splitters and the transmitters and receivers on the coherent transceivers can be used. This results in significant operational savings.

[0232] Figure 29Schematic diagram showing a WDM transport link 2900 that utilizes two unidirectional optical fibers 2902, 2904 to connect hardware-configured tunable coherent transceivers, transceiver 1 2906 and transceiver 2 2908, using non-filter-based combiners / splitters 2910, 2912, 2914, 2916 of the present teachings. The transmitter of transceiver 1 2906 is connected to the input port of combiner / splitter 2910 to send an optical signal to combiner 2912 via optical fiber 2902. The signal from the transmitter of transceiver 1 2906 is passed to the output port of combiner / splitter 2912 connected to the receiver of transceiver 2 2908. The transmitter of transceiver 2 2908 is connected to the input port of combiner / splitter 2916 to send an optical signal to combiner / splitter 2914 via optical fiber 2904. The signal from the transmitter of transceiver 2 2908 passes to the output port of the combiner / splitter 2914 connected to the receiver of transceiver 1 2906. Optional optical amplifiers 2918, 2920 may be added to the link to account for losses from the passive combiners / splitters 2910, 2912, 2914, 2916. Amplifiers may be placed anywhere between transceiver 1 2906 and transceiver 2 2908 to account for losses in the link as will be appreciated by those skilled in the art.

[0233] The high dynamic range of the coherent technology in the transceivers 2906, 2908 enables a passive combiner and splitter architecture using combiners / splitters 2910, 2912, 2914, 2916 without filters. Figure 29 Embodiments of link 2900 eliminate AWG and WSS costs and enable simple connections without the need for labeling or fiber numbering.

[0234] and Figure 29 The connection protocol method associated with the embodiment of link 2900 can be similar to utilizing Figure 28AThis system is similar to the AWG or WSS system of link 2800, but with some differences as described below. Fundamentally, link establishment is still based on the detection of a slow-scanned optical signal, the determination that the detected signal's duration is at least as long as the dwell time on a specific wavelength channel for the slow scan, and the detection of an optical signal whose duration is less than or equal to the dwell time on a specific wavelength channel for the fast scan. However, the protocol must account for the fact that light from all wavelength channels can reach all transceivers because the splitter / combiner does not provide filtering options. The connection protocol for a non-filtered splitter / combiner link utilizes a coherent receiver and a local LO laser as spectral detection of the far-side transmit carrier. At startup, the number of tuned channels is based on the splitter port count set in the database or set by the customer. This set of channels is scanned at the fast scan rate. Therefore, this channel count is used to represent the channel count for the full scan of the fast scan. The full fast channel scan time is the time required to scan through each of these channels using a short fast scan dwell time on each channel. The RF amplifier is turned off on the transmitter at startup so that the transmit power generates a continuous wave (CW) signal. The CW signal is slow-scanned to produce a sequence of CW wavelength channels, each with a specific slow-scan duration. The received power from the CW wavelength signal is simply the DC detection power, since there is no modulation on the CW wavelength transmitted by the local oscillator.

[0235] In operation, the far-side receiver uses RF detection and total power detection to determine when the near-side transmitter is unmodulated and tuned to a CW channel that it can receive because it is the same LO as the far-side receiver. The receiver then triggers a transmission of the same channel to the far-side. Both sides are now locked on the same channel, and the RF amplifiers are enabled to begin data transmission. If the CW carrier wavelength channel happens to be the same as a coherent channel already in service, the presence of this CW carrier will not affect the coherent traffic of the coherent channel already in service because only DC detection power is provided to the receiver. In these operating methods, the near-end and far-end transceivers have a master / slave definition for the far-side / near-side of the link because the connection protocol operates directionally.

[0236] Now, the following is described in more detail: Figure 29 An embodiment of a startup connection protocol method for a coherent link using a passive, non-filtering combiner is shown. For an embodiment using a master / slave method, the master transceiver is, for example, transceiver 2906 and the slave transceiver is transceiver 2908, but this designation is arbitrary. The RF amplifier is turned off in the transceiver on the near side of the link, generating a CW carrier at power-up.

[0237] Figure 30A3000 is shown as a spectrum generated by a transceiver in a powered-up state according to a method using a connection protocol according to the present teachings. This represents the spectrum of the signal generated by the CW LO at a specific wavelength channel. The transceiver to laser output power is only transmitted when the VOA or SOA is turned on. Figure 30B 3020, a spectrum generated by a transceiver in an established link operating state according to a method of connection protocol of the present teachings. This represents the spectrum of a signal generated by a transmitter on a particular channel with RF modulation turned on. Figure 30C A time series 3040 of spectra of a transceiver in a tuned state without RF modulation, representing a method of connection protocol of the present teachings. In these figures, different line types indicate different wavelength channels. Thus, Figure 30C represents the detection signal of the received light according to a slow scan including the LO. The transceiver scans for occupied channels on the optical fiber to which it is connected. The spectrum time series 3040 shows the unmodulated spectrum for four sequential wavelength channels, and then, after a predetermined period of time which may also be referred to as interval "T", another slow scan begins. In general, the slow scan will step through all the wavelength channels of the system. As an example, this may be 96 wavelength channels or 80 channels, depending on the particular WDM system. In some embodiments, a 16 channel splitter is used, and therefore, 16 channels are selected to represent the full scan for the protocol. Various embodiments use various numbers of channels. Figure 30D A time series 3060 of spectra of a link in a tuned state with RF modulation on channel 1 is shown according to a method of a connection protocol of the present teachings. Figure 30D = means that the first channel in the sequence has a modulated signal because the spectrum bandwidth is wide. This indicates to the transceiver that the channel is occupied by a data carrying channel.

[0238] Continuing with the description of the initiation connection protocol, the near-side receiver uses RF detection from the LO and a photodiode positioned in the coherent receiver behind the polarization splitter to look for a modulated channel. If no modulated channel exists, the receiver waits on channel 1. The slave transceiver powers up and begins tuning from channel 1. This causes the master receiver to detect the far-side LO on channel 1, thus initiating a beacon state to the master transmitter. The slave receiver detects the beacon from the master and turns on the RF amplifier, causing the modulated spectrum to be transmitted. The slave maintains channel 1, the master leaves the beacon state, and enters hold on channel 1. The master then turns on the RF amplifier, and a coherent link is established for channel 1.

[0239] In the event that a link is established on channel 1, the protocol will continue with another transceiver master / slave pair that will not affect the traffic on channel 1, as described further below. Scanning of the link will result in Figure 30Dspectral time series 3060 is shown in FIG, where a modulated signal is on channel 1 and is tuned by the master LO on the other channels. In this case, the master transmitter powers up and the master receiver detects RF modulation on channel 1. The master transmitter then skips channel 1 and continues tuning from channel 2. The slave transceiver powers up, detects modulation on channel 1, and skips to channel 2. The slave receiver sees power but no modulation on channel 2 and remains transmitting for the unmodulated channel 2. The master detects the LO from the slave on channel 2 and switches to channel 2 and enters the beacon state. The slave senses the beacon state on channel 2 and turns on the RF amplifier to generate a modulated signal. The master senses the RF modulated signal from the slave and turns on RF modulation for its transmitter, and a link is established on channel 2. The specific channels described are merely examples, and as one skilled in the art will appreciate, other channels can be used.

[0240] In some embodiments, transceiver modules are configured in master or slave mode and have different product numbers, for example, to distinguish them prior to shipment via internal database parameters. A master and slave transceiver module operate in pairs to form a link. However, in some embodiments, the master or slave designation is not required, and the transceiver at either the near or far end of the link can execute the protocol described herein without the master or slave designation. The master-configured module may support the use of vendor-defined "auto-tune configuration" registers for initiating the connection protocol. The master-side transceiver module is connected to or includes a host processor that knows the appropriate transmit channel configuration for the module. Slave-configured modules will begin in auto-tune mode upon a power cycle and / or power-on reset. Therefore, in some embodiments, auto-tune is a step in a method for implementing the connection protocol and initiates a slow tuning of the transmitter through a sequence of channels, where the transmitter remains on each channel for a specified duration before switching to the next channel in the sequence. This duration can vary. For example, in some embodiments, the duration is 1 second. In other embodiments, the duration is 5 seconds. In some embodiments, the channel sequence is a sequence that starts from a specific channel number on the ITU grid and steps one channel number at a time. For example, the sequence can start from channel 1 of the ITU grid, or the sequence can start from another channel of the ITU grid.

[0241] In some embodiments, the autotune startup or power-up process proceeds as described below. For the master module, the "transmitter discovery" command is asserted at power-up. A host processor in or connected to the module sets the appropriate transmit channel. If receive LOS is asserted, in other words, the receiver indicates LOS=1, the host processor writes to the "autotune configuration" register which begins the slow scan tuning mode. In slow scan mode, RF power is turned off and the transmitter transmits the local oscillator signal only on the channel to which it is tuned. The processor waits for RX_LOS (LOS=0) to clear. When RX_LOS is cleared, transmitter discovery mode is exited, modulation is turned on, and a link is established.

[0242] For slave modules, transmitter discovery is asserted at power-up. A five-second per-channel slow channel tuning process begins, with the tuned channel set to the last set channel. If RX_LOS is cleared, tuning is paused. Otherwise, if RX_LOS is asserted, the method continues by tuning to the next channel. The current transmit channel is stored. Once tuning is paused, RF modulation is turned on and a link is established.

[0243] In some embodiments, an existing link is established by the slave. In these embodiments, with the transmit channels stored in the slave, the first channel tuned will establish the link and the master will immediately exit tuning mode and enter normal operation. In this case, the slave asserts transmit discovery mode, TX_DIS, at power-up, and a slow tuning channel process begins, where tuning starts from the last set channel. If RX_LOS is clear, tuning is stopped. If RX_LOS (LOS=0) is asserted, the method tunes to the next channel. The current channel is then stored, tuning mode is terminated, and modulation is initiated, thereby establishing the link.

[0244] In an embodiment where the existing link is established by a slave, the master-side module proceeds as follows. In the master module, TX_DIS is asserted at power-up. The host processor sets the appropriate TX channel. If RX_LOS (LOS=0) is off, the processor skips setting the "Autotune Configuration" register. TX_DIS is turned off. The link is established and autotune mode is not entered or required. For the slave, autotune is complete. The module is in normal operation.

[0245] In some embodiments, a new slave module is installed and the process is as follows. For the master, slow tuning is completed and the link is established. The master module is in normal operation. If the host processor detects that RX_LOS (LOS=0) is asserted within "x" time, the host writes the "Autotune Configuration" register to start autotune mode. The transmitter discovery mode TX_DIS is then asserted. The host waits for RX_LOS (LOS=0) to be deasserted or cleared. When RX_LOS (LOS=0) is deasserted or cleared, then TX_DIS is deasserted. Autotune mode is exited and normal operation continues. Autotune is then completed and the link is established.

[0246] When a new slave module is installed, the process is as follows. TX_DIS is asserted at power-up. The slow channel tuning process begins with five seconds per channel, starting from the last set channel or the first channel. If RX_LOS (LOS=0) is deasserted, the auto-tune stops. Otherwise, if RX_LOS (LOS=0) is asserted, the method tunes to the next channel. The current TX channel is stored after RX_LOS (LOS=0) is deasserted. Auto-tune mode is then exited and normal operation continues. Auto-tune is completed and the link is established.

[0247] Some embodiments of the present teachings utilize a non-filtering splitter to connect a transceiver to a device that combines optical signals onto a link fiber to provide a bidirectional connection with a reduced component count. The device that combines optical signals onto the link fiber can be filtered or unfiltered. The use of a passive splitter connected to the transceiver transmitter and receiver reduces the number of combiner components by half for a bidirectional link. In some embodiments, the fiber optic link includes an optical amplifier. In other embodiments, no amplifier is used.

[0248] Some embodiments do not use the master / slave designation described above. In some of these embodiments, the two sides ping-pong the routine until the LO fast scan for search overlaps with the TX CW onset. That is, the two sides alternate between sending a slow LO scan and performing a LO fast scan to search for an incoming wavelength match until a short pulse of nominally a duration equal to the fast scan dwell time is detected. The link is then established, and client data traffic can flow.

[0249] Figure 31A schematic diagram of a WDM transmission link 3100 according to the present teachings is shown. The WDM transmission link 3100 utilizes transceivers 3102 and 3104 in a coherent hardware configuration with AWG filters. The output of a coherent transmitter 3106 is connected to a port of a 1x2 splitter 3108. The input of a coherent receiver 3110 is connected to the second port of the 1x2 splitter 3108. The third port of the 1x2 splitter 3108 is connected to an AWG filter 3112. The AWG filter 3112 combines light from each input port onto an optical fiber 3114 connected to an AWG filter 3116. The optical fiber 3114 carries bidirectional optical traffic. The output port of the AWG filter 3116 is connected to one port of a 1x2 splitter 3118. A coherent receiver 3120 is connected to the other port of the 1x2 splitter 3118. A coherent transmitter 3122 is connected to the third port of the 1x2 splitter 3118. In some embodiments, the transceivers 3102, 3104 can be located remotely from the AWGs 3112, 3116, for example, up to several kilometers away. This can be referred to as a remote PHY configuration. The AWGs 3112, 3116 do not tune or change filtering. The AWGs 3112, 3116 filter the wavelength channels.

[0250] In a WDM transport link 3100, both sides of the link require transceivers 3102 and 3104 to operate on the same wavelength channel, as the wavelength must pass through the filters of AWGs 3112 and 3116. This also requires that transceivers 3102 and 3104 operate at overlapping times to establish a connection. Using a master / slave technique, one of transceivers 3102 and 3104 is tuned quickly, while the other is tuned slowly. This provides overlap and detection on both sides of the link 3100. Handshaking is used in this process to close the coherent link, taking into account the filters of AWGs 3112 and 3116 in the link 3100.

[0251] Figure 32A schematic diagram of a WDM transmission link 3200 according to the present teachings is shown. The WDM transmission link 3200 utilizes transceivers 3202 and 3204 in a coherent hardware configuration with a passive splitter without filtering. Link 3200 uses passive splitters 3206 and 3208 to combine the optical signals from transceivers 3202 and 3204. Link 3200 operates bidirectionally over an optical fiber 3210. The output of a coherent transmitter 3212 is connected to a port of the passive splitter 3206. The input of a coherent receiver 3216 is connected to a second port of the passive splitter 3206. Passive splitters 3206 and 3208 do not have wavelength filtering. Splitter 3206 combines and / or splits light from each port onto an optical fiber 3210 connected to splitter 3208. A coherent receiver 3220 is connected to a first port of splitter 3208. A coherent transmitter 3222 is connected to a second port of splitter 3208. In some embodiments, for a remote PHY configuration, the transceivers 3202, 3204 are located remotely from the corresponding splitters 3206, 3208, for example, up to several kilometers away.

[0252] In combination Figure 32 During the discovery process of the embodiment of link 3200 described, transmitters 3212 and 3222 are powered on, search through established links, and check for established links. Discovery must also operate with one transmitter powered on and the far-side transmitter powered off. Power-on search is provided by using the variable optical attenuator (VOA) in transceiver 3202 to darken the local oscillator (LO). This step prevents the LO signal from coupling to utilized channels. Receiver 3220 in transceiver 3204 then scans through the receiver mixer and RF detection to find any occupied channels. Any occupied channels found are not used. Next, the VOA is activated in transceiver 3202 and transmitter 3212 scans for unoccupied channels using the local LO while simultaneously detecting the far-side LO in receiver 3220.

[0253] The connection algorithm operates with multiple transmitters (not shown) connected to the link 3200 operating simultaneously. The passive splitter coherent architecture of the link 3200 is relatively simple to connect. There is no need to mark any TX or RX fibers and no need to align to any specific passive ports. This allows the link to be established and the PHY layer for the data center to be built without any higher layer software connection protocols. In some embodiments of non-filtered links using coherent SFP+ transceivers, separate and different controls separate from the SFP+ must be used to support the passive splitter architecture and reduce cabling and ADD / DROP costs. These embodiments will be specifically targeted at low channel count coherent traffic use cases.

[0254] A feature of the present teachings is that the signaling for discovery of unfiltered WDM links can be performed without complex higher layer communication protocols. Instead, simple variations using only fast and slow tuning of the transceiver and / or components in the link are used. These systems utilize a coherent receiver and a local LO laser as a spectral detector for the presence of a far-side transmitter carrier. At startup, the number of wavelength channels tuned is based on the splitter port count. This can be set, for example, in a database or by the customer. The RF amplifier is disabled on the transmitter at startup. In addition, the semiconductor optical amplifier and / or variable optical attenuator (SOA / VOA) is disabled on the transmit side to eliminate any contention when the far-side receiver scans for existing channels. The far-side receiver scans using the local LO laser to mix and observe valid channels, and also uses RF detection for modulation and to find occupied channels.

[0255] In some embodiments, a specific connection routine is used for receiver scanning, transmitter setup, and wait states for the far-side connection to be established. This includes a specific framework that enables fast and slow techniques for tunable lasers to establish connections without complex protocols. The contention avoidance process is similar to legacy, low-layer Ethernet copper connection management and collision avoidance techniques. However, in embodiments of methods according to the present teachings, these techniques are applied to coherent optical links that propagate multiple wavelengths.

[0256] The steps of a method for establishing a link in a hardware configuration comprising a non-filtering splitter and a coherent transceiver according to the present teachings generally include searching for occupied channels and CW-LO signals by tuning the LO in the coherent receiver. The method also includes the steps of modulating an optical signal with a coherent transmitter and scanning the CW-LO channels using a specific time sequence. Other steps include determining occupied channels and removing those channels from the transmitter scan of CW-LO channels in a subsequent scan, determining, at the transceiver pair, the channel through which the link is to be established based on the overlap of the CW-LO channels and the reception of an unmodulated LO carrier mixed with a specific LO channel in the receiver, and performing RF modulation on the determined channel to establish the link. As will be apparent to those skilled in the art from the following example description of the operation of the method, in various embodiments of the present teachings, these steps may be performed separately, or some or all may be performed simultaneously. The steps may also be implemented in some or all of the transceivers connected to a particular link, and these steps may be performed separately or simultaneously on the various transceivers.

[0257] Refer back Figure 30A-B, the spectrum 3000 of the transmitter with the RF amplifier turned off is shown as distinct from the spectrum 3020 of the transmitter with the RF amplifier turned on. To generate spectrum 3000, the RF amplifier is turned off, resulting in a single CW carrier signal spectrum. The SOA is turned on and in the "up" state. To generate spectrum 3020, the RF amplifier is turned on, providing data modulation on the CW carrier and allowing data to flow over the link. This feature, which determines the difference between the received spectrum 3020 with modulation bandwidth and the CW LO spectrum 3000 without modulation bandwidth, is used by the transceiver both to avoid using occupied channels and to establish channels to initiate a link as described further below. This differentiation capability is readily achieved, for example, using detection, mixing, and processing available in standard telecommunications receivers.

[0258] Figure 33A A time series 3300 of spectra of a transceiver in a tuned state without RF modulation represents an embodiment of a method of connecting a protocol according to the present teachings. The far-end transceiver tunes the LO at the receiver to mix with the incoming signal, searching for an occupied channel. Figure 33B A spectrum time series 3320 is shown illustrating an embodiment of a method of using a connection protocol according to the present teachings, showing how a transceiver without RF modulation can be tuned to avoid collisions using wait times between sequences. Each starting wavelength 3322 is repeated at a specific period 3324 in a given transmitter to eliminate collisions between other transmitters hooked to the near side of the link. Figure 33C 3340 shows the spectrum of the transceiver with RF modulation after successful completion of the connection in a method according to the connection protocol of the present teachings. The near-end transmitter is turned on, the link is established, and client data traffic is being sent over the link.

[0259] A feature of the present teachings is that the timing sequences of the LO fast scan and slow scan tuning for search tuning can be configured to achieve various purposes. For example, one purpose is to enable a single laser in a transceiver package to perform both a LO fast scan for searching using a transceiver receiver and a LO slow tuning sent to another transceiver to determine the wiring connection and the wavelength channel for the connection. Other purposes include exploiting the scalability of channel counts. For example, the timing sequence should be such that even if the channel count is small, it can quickly converge to a specific link connection and wavelength channel, and also be able to search over relatively more channels. For example, in various embodiments, the system can operate with as few as 1 or 2 channels and as many as 16 channels. In principle, the present teachings are not limited to a specific number of channels. It is desirable that the embodiments of the present teachings converge quickly for various channel counts. As a result, the present teachings are compatible with various timing sequences (including those described in detail herein).

[0260] Figure 34A Spectral time series 3400, 3420, associated with the status of the search and connection steps, represent an embodiment of a method for a connection protocol according to the present teachings. Different line types represent different spectral components for different wavelength channels. An LO search step, using a generated rapid scan 3402 in the context of spectral time series 3400, is used to determine occupied channels as described herein. Spectral time series 3400 is generated by a local oscillator laser in the receiver and is not transmitted along the link. As described earlier, a rapid scan involves scanning the wavelength channels in the system, with a relatively short dwell time on each channel and a total channel scan time that is the time it takes to step through each channel. This generated rapid scan signal is used within the transceiver that generates it. Specifically, the generated rapid scan signal is mixed with the incoming signal to the receiver. The LO search step mixes the LO scanned spectral time series 3400 with any light present at the input of the far-side receiver in the receiver mixer and detects the optical signal from the mixer. The receiver mixer generates a mixed receive signal only when the LO wavelength channel generated by the receiver matches the wavelength channel of the optical signal input to the receiver. Therefore, a detection signal is generated only when the wavelength channel of the optical signal at the mixer input matches the LO wavelength channel generated by the receiver laser. The detection signal, at the matching wavelength, is further analyzed to determine its modulation bandwidth.

[0261] A spectral time series 3400 of the LO search step is shown, where the far-side transceiver generates a rapid scan 3402 using a rapid scan of the receiver LO, which includes a short-duration scan that iterates through each of a predetermined number of channels. For example, in some embodiments, as shown, four channels are scanned. Generally, the number of channels scanned depends on the characteristics of the splitter used. For example, a 1x4 splitter would equate to four scanned wavelengths. Larger port splitter sizes will support more wavelengths.

[0262] The detected modulation bandwidth of the mixing signal is used to identify the optical signal at the receiver's input. A large modulation bandwidth indicates an occupied channel. In contrast, a continuous-wave local oscillator signal has no perceptible modulation bandwidth. Therefore, a relatively small or negligible modulation bandwidth indicates a continuous-wave local oscillator signal.

[0263] Using the measured modulation bandwidth of the mixing signal allows the system to identify transmitter channels that can form a link connection between a pair of transceivers. The unmodulated signals used to identify link channels are distinguished from occupied channels at the receiver because they lack modulation bandwidth. Therefore, RF detection at the far-side receiver indicates which channels are occupied via coherent modulation because they exhibit RF modulation bandwidth. If occupied channels are identified, any occupied channels are discarded from the subsequent long-duration TX_ON state scan. However, all channels are typically scanned during the LO search step. This scan allows determination of channel or fiber disconnects. In some embodiments, LO search step T1 3404 has a duration of approximately 100 ms per channel, and the system scans four channels. Therefore, for n=4, T1 = 400 ms. In some embodiments, the LO search step interval T 3406 is approximately 2*m*T1, where m = unoccupied channels. Therefore, interval T 3406 shortens as channels are determined to be occupied.

[0264] In the TX_ON state, the transmitter is on with a CW unmodulated LO signal applied to an unoccupied channel, initiating a LO slow scan spectrum time sequence 3420. The scan interval T4 3426 and wavelength channel dwell duration T3 3424 of the sweep of the CW LO signal across the channels are set to avoid collisions with other transmitters and to ensure overlap with the receive LO search fast scan on the receive side of the link. Figure 34A In the illustrated embodiment of the method, the near-side transmitter sweeps the CW LO signal through the first wavelength channel 3422 for a duration of T3 3424. In some embodiments, time T3 3424 is approximately three times T1 3402. The near-side transmitter waits for a period of time T4 3426 before changing to the next wavelength channel 3428. T4 3426 can be a random time. In some embodiments, time T4 3426 is approximately 2*n + / - rand*T1, where rand = random time up to n*T1. The random time between different channels sent to the far-side transceiver enables connection closure and overlapping LO searches. As the number of channels increases, it is crucial to keep T1 short to increase link closure time.

[0265] Figure 34BSpectral time series 3430 related to the state of a transceiver and an associated LO laser, representing an embodiment of a method of using a connection protocol in accordance with this teaching. The transceiver uses a single laser for both LO search and for communication at the far end over an optical fiber link. The LO search occurs in some embodiments when LOS is asserted in the transceiver. Trace 3432 represents a slow sweep of the LO sending an LO signal over the link, where one transmission period for one wavelength channel is shown. The transceiver LO search fast sweep is represented in trace 3434. The local receiver uses a fast sequence to sweep possible channels to determine if a signal exists on any of the channels incoming to the receiver. Trace 3436 shows a composite view of the use of a particular LO laser for the combination of receiver search and far-end communication. The LO search fast sweep occupies a duration T1, followed by an interval T before the slow sweep of the channels is transmitted. The transmit channel slow sweep stays for a duration T3, followed by a wait interval T4.

[0266] In some embodiments, T1 is a duration such that short pulses for each channel can be swept in the LO search fast sweep. The time T3 is equal to 3 times T1. The time T is equal to 2 times the number of channels times T1, T2 is T1 plus the number of channels times a random number times T1, where the random number is between 0 and 0.99. The time T4 is T minus the sum of T2 and T3. For example, if the channel count is 4: T1 = 100 ms, T = 800 ms, T3 = 300 ms, 100 ms < T2 < 396 ms, 104 ms < T4 < 400 ms. As another example, for a channel count of 3: T1 = 100 ms, T = 600 ms, T3 = 300 ms, 100 ms < T2 < 297 ms, 3 ms < T4 < 400 ms.

[0267] In trace 3436 Figure 34B the representation of the timing sequence shows how it can perform a receive LO search fast sweep and a transmit slow channel sweep using a single laser in the transceiver.

[0268] Figure 35 A set of time series 3500 representing an embodiment of a method of using a connection protocol in accordance with this teaching for a non-filtered optical link showing search and detection. The time series 3500 optionally includes a direct detection time series and includes a spectral sequence. Different line types are utilized for the same use of different wavelength channels as Figure 35 in Figure 34A -B. A representation of the TX_ON_1 state spectral time series trace 3502 is shown, where for the proximal transceiver (also referred to as transceiver 1), the slow sweep sequence is initiated in the on state. The spectral sequence associated with the LO search in transceiver 1 is represented in trace 3504. Note that as combined with Figure 34A As described in FIG-B, in some embodiments, a single laser LO can generate the tuning sequence shown in traces 3502 and 3504. Also shown for the far-side transceiver (also referred to as transceiver 2) is a TX_ON_2 state spectrum time series trace 3506 in the on state. The temporal received power from direct detection is shown in direct detection time series trace 3508. The spectrum sequence associated with the LO search in transceiver 2 is shown in trace 3510. The direct detection time series for the receiver in transceiver 2 is shown in trace 3512.

[0269] Both transmitters initiate a search sequence upon power-up, which is shown at the beginning of time series traces 3504 and 3510. Note that the designations "near side" and "far side" are used solely for clarity to distinguish between the two sides of the link. The system operates bidirectionally without any specific designation of the near side and / or far side of the link.

[0270] In operation, when transceiver 2 begins transmitting optical signals 3514 to slowly traverse a channel scan and transmits them to the link using its spectral time sequence of trace 3506, direct detection in the near-side receiver detects light 3516 as shown in trace 3508, but does not distinguish a specific channel. Similarly, when the near-side transceiver begins transmitting optical signals 3518 in its spectral time sequence 3502, in a slow scan across channels, direct detection in the far-side receiver spectral time sequence 3512 detects light 3520, but does not distinguish a specific channel. However, the next tuned channel 3524 in the slow scan from transceiver 2 is picked up by the receiver in transceiver 1. This is shown at region 3522, which shows the overlap of the slowly scanned channel 3524 and its match with the LO search fast scan channel in trace 3504. Therefore, when the LO search sweep in transceiver 1 overlaps with the matching LO channel 3524 from the slow scan of transceiver 2, that channel is selected. An "ACK" pulse is generated. Transceiver 1 and transceiver 2 turn on RF modulation on that channel, and the link is established. After any RF amplifiers are turned on for a particular channel, that particular channel is now "UP" and is discarded from subsequent LO searches.

[0271] For the combination Figure 34A The described search scan of the unmodulated channels is repeated in association with the described framing sequence of intervals T1, T, T3, and T4 to prevent collisions or channel overlap. Figure 36ASpectral timing diagram 3600 showing an embodiment of a link establishment method for a coherent link with a non-filtering passive splitter / combiner according to the present teachings. LO search trace 3602 shows timing characterized by the search interval T1, and the interval T between searches. The LO fast scan search sequence has a period T5 = T1 + T. Slow scan trace 3604 shows timing characterized by the duration of the dwell time on the slow scan channel, 3*T1, and the interval T before tuning to the next channel at a random time. rand (which is chosen to avoid conflict with the LO search fast scan) characterization. For example, T rand Combined with Figure 34A -B description of T4 can be the same. Figure 36B express Figure 36A Combined spectral timing diagram 3650 of an embodiment of a link establishment method for a coherent link with a non-filtering passive splitter / combiner. Figure 36B This shows how the timing allows a single laser to switch between a local oscillator receive search for an incoming channel using a fast scan of the LO and a transmitted slow scan signal, since there is no overlap of channel transmissions. That is, since T is fixed relative to T1, the LO is on for one side of the channel for 3*T1 during the slow scan channel dwell time, and this is at T rand So the probability of overlapping to close the link increases.

[0272] A key feature of the systems and methods for configuring optical network components for optical links and other hardware configurations is the use of both slow and fast wavelength scans to exchange information between components. The relative timing of these scans allows components to identify each other and also allows for the determination of various other aspects of the link configuration, such as establishing a link, sending client data traffic over the link, and transmitting other component configuration information. Accordingly, the present teachings describe wavelength scanning, which includes slow and fast scans that are used together to support various embodiments of protocols for link setup. A wavelength scan is a scan of wavelength channels in a particular system, characterized by a specific dwell time on each channel and a complete channel scan time, which is the time it takes to scan all channels in the system, given the specific dwell time for each channel. An important feature that ensures convergence of the protocol is the relative timing of the slow and fast scans. Generally speaking, a slow scan is a scan in which the dwell time on a particular wavelength channel is as long as or longer than the duration of a complete scan of the wavelength channel in a fast scan.

[0273] The slow scan and fast scan timing parameters are selected so that based on the detection of the slow scan and fast scan signals and the determination of the duration of the detection light, elements in the link can be configured. For example, in a link with two transceivers, the detection of an optical pulse with a duration equal to the dwell time on a specific wavelength channel for the fast scan, and the detection of a signal from the link with a duration equal to the dwell time on the specific wavelength channel for the slow scan, allows the transceivers on both sides of the link to automatically configure the link and transmit client data traffic. Various embodiments of the system determine the detection of an optical pulse with a duration equal to the dwell time on a specific wavelength channel for the fast scan, and the detection signal from the link with a duration equal to the dwell time on the specific wavelength channel for the slow scan, in various manners as described herein.

[0274] equivalent

[0275] Although the applicant's teachings are described in conjunction with various embodiments, the applicant's teachings should not be limited to such embodiments. On the contrary, as those skilled in the art will appreciate, the applicant's teachings encompass various alternatives, modifications, and equivalents that can be made thereto without departing from the spirit and scope of the present teachings.

Claims

1. An optical transceiver, comprising: a) a tunable transmitter having an electrical input and an optical output, the tunable transmitter being configured to generate an optical transmit signal at the optical output for performing at least one of the following: 1) slow scanning of the wavelength channels, including sequential emission of an optical signal in each wavelength channel during a first dwell time of each wavelength channel; and 2) rapid scanning of wavelength channels, including sequential transmission of optical signals in each wavelength channel within a second dwell time of each wavelength channel, wherein the first dwell time is equal to or greater than the sum of the second dwell times of all wavelength channels; b) a receiver having an electrical output and an optical input, the receiver receiving an optical receive signal in a receive wavelength channel, the optical receive signal indicating one of the following: 1) slow scanning of the receive wavelength channels by the remote optical transceiver; and 2) a fast scan of the receive wavelength channels by the remote optical transceiver during a slow scan of the transmit wavelength channels by the tunable transmitter; and c) a processor having an input connected to the electrical output of the receiver and an output connected to the electrical input of the tunable transmitter, wherein the processor instructs the tunable transmitter to: performing a fast scan of wavelength channels with a second dwell time for each wavelength channel in response to the slow scan of the receive wavelength channels by the remote optical transceiver; and A communication link is established with a remote optical transceiver in a transmit wavelength channel in response to the fast scan of the receive wavelength channel being received from the remote optical transceiver during the slow scan of the transmit wavelength channel.

2. The optical transceiver of claim 1, wherein the receiver comprises a direct detection receiver. The optical transceiver of claim 1 , wherein the receiver comprises a coherent receiver.

4. The optical transceiver of claim 1, wherein the processor instructs the tunable transmitter to perform the slow scan of the wavelength channels upon startup of the transceiver.

5. The optical transceiver of claim 1, wherein the processor instructs the tunable transmitter to perform the slow scan of the wavelength channels when the transceiver is powered on.

6. The optical transceiver of claim 1, wherein the processor instructs the tunable transmitter to perform the slow scan of the wavelength channels after an idle state of the transceiver. 7 . The optical transceiver of claim 1 , wherein the processor instructs the tunable transmitter to perform the slow scan of the wavelength channels upon a loss of signal (LOS) indication.

8. The optical transceiver according to claim 1, wherein: The tunable transmitter establishes the communication link in the transmission wavelength channel by generating an optical transmission signal indicative of a beacon in the transmission wavelength channel.

9. The optical transceiver of claim 1, wherein the receiver is further adapted to receive an optical receive signal indicative of a beacon in the receive wavelength channel transmitted from a remote optical transceiver in response to a rapid scan of the transmit wavelength channel by the tunable transmitter.

10. The optical transceiver of claim 9, wherein the processor instructs the tunable transmitter to perform a slow scan of the wavelength channels in response to the beacon received from the remote optical transceiver.

11. The optical transceiver according to claim 1 , wherein the tunable transmitter is further configured to have a HOLD state for stopping the scanning at a current wavelength channel, and wherein the processor instructs the tunable transmitter to enter the HOLD state when determining that the optical reception signal exceeds a threshold. The optical transceiver of claim 11 , wherein the threshold comprises a power threshold. The optical transceiver of claim 11 , wherein the threshold comprises a duration threshold.

14. The optical transceiver of claim 11, wherein the processor instructs the tunable transmitter to generate transmission of real-time traffic after entering the HOLD state.

15. The optical transceiver of claim 1, wherein at least one of the slow scan of wavelength channels and the fast scan of wavelength channels comprises a scan of wavelength channels traversing an ITU grid.

16. The optical transceiver of claim 1, wherein at least one of the slow scan of wavelength channels and the fast scan of wavelength channels comprises a scan through a predetermined number N of wavelength channels.

17. The optical transceiver of claim 1, wherein the tunable transmitter is further configured to have a BEACON state in which a dwell time at a current wavelength channel is less than the first dwell time of each channel.

18. An optical transceiver, comprising: a) a tunable transmitter having an electrical input and an optical output, the tunable transmitter being configured to generate an optical transmit signal at the optical output for performing a slow scan of the wavelength channels, the slow scan of the wavelength channels comprising sequential transmission of an optical signal in each wavelength channel within a first dwell time of each wavelength channel; b) a receiver having an electrical output and an optical input, the receiver receiving an optical receive signal in a receive wavelength channel, the optical receive signal indicating a fast scan of the receive wavelength channel within a second dwell time by a remote optical transceiver during a slow scan of the transmit wavelength channels by the tunable transmitter, the first dwell time being equal to or greater than a sum of the second dwell times of all wavelength channels; as well as c) a processor having an input connected to the electrical output of the receiver and an output connected to the electrical input of the tunable transmitter, wherein the processor instructs the tunable transmitter to establish a communication link with a remote optical transceiver in a transmit wavelength channel in response to a fast scan of the receive wavelength channel received from the remote optical transceiver during a slow scan of the transmit wavelength channel.

19. An optical transceiver, comprising: a) a tunable transmitter having an electrical input and an optical output, the tunable transmitter configured to generate an optical transmit signal at the optical output for performing a rapid scan of the wavelength channels, the rapid scan of the wavelength channels comprising sequential transmission of an optical signal in each wavelength channel within a second dwell time of each wavelength channel; b) a receiver having an electrical output and an optical input, the receiver receiving an optical receive signal in a receive wavelength channel, the optical receive signal indicating a slow scan of the receive wavelength channel by a remote optical transceiver for a first dwell time, the first dwell time being equal to or greater than a sum of second dwell times of all wavelength channels; as well as c) a processor having an input connected to the electrical output of the receiver and an output connected to the electrical input of the tunable transmitter, wherein the processor instructs the tunable transmitter to perform a fast scan of wavelength channels with a second dwell time for each wavelength channel in response to the slow scan of the receive wavelength channels by the remote optical transceiver.

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