Method and apparatus for hardware-configured network

Abstract

To provide a hardware-configured network.SOLUTION: An optical network element for a hardware-configured optical network comprises a first optical port that receives an input optical signal including reception control information from the hardware-configured optical network. A demodulator optically coupled to the first optical port decodes the reception control information for configuring the optical network element. A modulator having an electrical modulation input that receives transmission control information performs modulation on an optical carrier, thereby generating a transmission optical control signal representing the transmission control information. A second optical port transmits the transmission optical control signal representing the transmission control information to the hardware-configured optical network.SELECTED DRAWING: Figure 8

Description

[Background technology]

[0001] The 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.

[0002] (introduction) The growing need for high capacity data transmission over optical fibers, along with an increasing number of optical network elements being flexibly and dynamically networked together, presents significant challenges to the optical fiber telecommunications industry. For example, the demand for higher capacity requires that more transceiver wavelengths be spaced more closely together in the spectral domain to provide higher capacity over a single fiber or connection. These high capacity and high channel count systems call for more real-time performance data monitoring to control the transceivers. Furthermore, the greater number of transceivers required for these high capacity and high channel count systems calls for more automation of transceiver configuration to improve reliability and reduce human interaction. In addition, configuring networks to include an increased number and variety of optical elements, including transceivers, amplifiers, wavelength filters, wavelength multiplexers, wavelength demultiplexers, cross-connect devices, optical switches, passive splitters, and combiners, calls for automation and control schemes capable of operating across a variety of optical element types.

[0003] For high capacity and high channel count systems, it is desirable to have automated configuration that allows network elements to self-provision and self-monitor in order to reduce the burden on network operations personnel during network tuning and ongoing operation. Automation allows larger optical networks to be built and operated at lower cost.

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

[0005] Furthermore, scaling optical communication systems to achieve high capacity and channel counts requires that expanded configuration capabilities be provided within the same or a smaller footprint than currently deployed optical communications. It is therefore desirable to reuse and / or rely heavily on existing network element components for configuration methods and apparatus. Summary of the Invention [Means for solving the problem]

[0006] The present specification also provides, for example, the following items: (Item 1) 1. An optical network element for a hardware configured optical network, the optical network element comprising: a) a first optical port that receives an input optical signal from the hardware-configured optical network, the input optical signal including receive control information; b) a demodulator having an input optically coupled to the first optical port, the demodulator decoding the received control information to configure the optical network element; and c) a modulator having an electrical modulation input for receiving transmission control information, said modulator modulating an optical carrier to thereby generate a transmission optical control signal representative of said transmission control information; d) a second optical port for transmitting the transmission optical control signal representing the transmission control information to the hardware-configured optical network; 1. An optical network element comprising: (Item 2) 2. The optical network element of claim 1, wherein the optical carrier comprises at least one of client data traffic, dummy traffic, a CW optical signal, and amplified spontaneous emission light. (Item 3) 2. The optical network element of claim 1, wherein the optical carrier comprises one of a plurality of wavelengths. (Item 4) Item 2. The optical network element of item 1, wherein the optical carrier comprises a band of wavelengths. (Item 5) 2. The optical network element of claim 1, wherein the received control information is amplitude modulated onto the input optical signal. (Item 6) 2. The optical network element of claim 1, wherein the received control information is phase modulated onto the input optical signal. (Item 7) 2. The optical network element of claim 1, wherein the modulator performs amplitude modulation on the optical carrier, thereby generating an amplitude modulated transmission optical control signal representing the electrical transmission control information. (Item 8) 2. The optical network element of claim 1, wherein the modulator performs phase modulation on the optical carrier, thereby generating a phase modulated transmission optical control signal representing the electrical transmission control information. (Item 9) 2. The optical network element of claim 1, wherein a modulation frequency of the received control information is less than a frequency of client data modulation on the optical signal. (Item 10) 2. The optical network element of claim 1, wherein the modulation frequency of the transmitted optical control signal is less than the frequency of client data modulation on the optical signal. (Item 11) Item 2. The optical network element of item 1, wherein the optical network element comprises a wavelength selective switch. (Item 12) 2. The optical network element of claim 1, wherein the optical network element comprises an optical channel monitor. (Item 13) 2. The optical network element of claim 1, wherein the optical network element comprises an optical amplifier. (Item 14) 2. The optical network element of claim 1, wherein the optical network element comprises a programmable filter. (Item 15) Item 2. The optical network element of item 1, wherein the optical network element comprises a transceiver. (Item 16) Item 2. The optical network element of item 1, wherein the optical network element comprises a wavelength multiplexer / demultiplexer. (Item 17) Item 2. The optical network element of item 1, wherein the optical network element comprises a wavelength cross-connect device. (Item 18) 2. The optical network element of item 1, wherein the optical carrier is generated by the optical network element. (Item 19) 2. The optical network element of claim 1, wherein at least one of the receive and transmit control information includes digital diagnostic data. (Item 20) 20. The optical network element of item 19, wherein the digital diagnostic data includes at least one of a transmitter channel identification number, a receiver channel identification number, optical channel monitor calibration data, optical network element calibration data, and optical element alarm threshold data. (Item 21) Item 2. The optical network element of item 1, wherein the first optical port and the second optical port are the same optical port. (Item 22) 2. The optical network element of item 1, further comprising an electronic port for receiving the transmission control information for configuring the hardware configuration network. (Item 23) Item 1. The optical network element of item 1, further comprising a control processor that receives the decoded received control information and configures the optical network element in response to the decoded control information. (Item 24) 1. An optical network element for a hardware configured optical network, the optical network element comprising: a) a first optical port for receiving an input optical signal from the hardware configured optical network; b) a modulator having an electrical modulation input for receiving transmission control information, said modulator performing modulation on said input optical signal to thereby generate a transmission optical control signal representative of said transmission control information; c) a second optical port for transmitting the transmission optical control signal representing the transmission control information to the hardware-configured optical network; 1. An optical network element comprising: (Item 25) 25. The optical network element of claim 24, wherein the input optical signal includes at least one of client data traffic, dummy traffic, a CW optical signal, and amplified spontaneous emission light. (Item 26) Item 25. The optical network element of item 24, wherein the input optical signal comprises one of a plurality of wavelengths. (Item 27) 25. The optical network element of claim 24, wherein the input optical signal comprises a band of wavelengths. (Item 28) 25. The optical network element of claim 24, wherein the modulator performs amplitude modulation on the input optical signal to thereby generate an amplitude modulated transmit optical control signal representative of the electrical transmit control information. (Item 29) 25. The optical network element of claim 24, wherein the modulator performs a phase modulation on the input optical signal, thereby generating a phase modulated transmit optical control signal representative of the electrical transmit control information. (Item 30) 25. The optical network element of claim 24, wherein the modulation frequency of the transmit optical control signal is less than a frequency of client data modulation on the input optical signal. (Item 31) 25. The optical network element of claim 24, wherein the transmission control information includes digital diagnostic data. (Item 32) Item 32. The optical network element of item 31, wherein the digital diagnostic data includes at least one of a transmitter channel identification number, a receiver channel identification number, optical channel monitor calibration data, optical network element calibration data, and optical element alarm threshold data. (Item 33) 1. A method of configuring an optical network element in a hardware configured optical network, the method comprising: a) receiving an optical signal from the hardware-configured optical network, the optical signal including receive control information; b) demodulating the received control information from the hardware configured optical network; and c) configuring said optical network element according to said demodulated received control information; and d) modulating transmission control information onto an optical carrier, thereby generating a transmission optical control signal representative of said transmission control information; e) transmitting the transmission optical control signal representing the transmission control information on the optical carrier to the hardware configuration network; A method comprising: (Item 34) 34. The method of claim 33, wherein modulating transmission control information onto the optical carrier includes generating the optical carrier from at least one of dummy traffic, a CW optical signal, and amplified spontaneous emission light. (Item 35) 34. The method of claim 33, wherein modulating transmission control information onto the optical carrier includes generating the optical carrier from one of a plurality of wavelengths. (Item 36) 34. The method of claim 33, wherein modulating transmission control information onto the optical carrier includes generating the optical carrier from one of a plurality of wavelengths of the received optical signal. (Item 37) Item 34. The method of item 33, wherein the received control information from the hardware configured optical network is amplitude modulated. (Item 38) Item 34. The method of item 33, wherein the received control information from the hardware configured optical network is phase modulated. (Item 39) Item 34. The method of item 33, wherein modulating the transmission control information includes amplitude modulating the transmission control information. (Item 40) Item 34. The method of item 33, wherein modulating the transmission control information includes phase modulating the transmission control information. (Item 41) Item 34. The method of item 33, wherein a modulation frequency of the received control information from the hardware configured optical network is less than a frequency of client data modulation on the optical network. (Item 42) Item 34. The method of item 33, further comprising amplifying the received optical signal and transmitting the amplified received signal accompanied by at least one of receive control information and transmit control information to the hardware configuration network. (Item 43) Item 34. The method of item 33, further comprising monitoring a portion of the received optical signal and transmitting a remaining portion of the received signal to the hardware configuration network. (Item 44) Item 34. The method of item 33, further comprising switching the wavelength of the received optical signal to a particular channel within the hardware configured network. (Item 45) 34. The method of claim 33, further comprising multiplexing / demultiplexing wavelengths of the received optical signals onto specific channels within the hardware-configured network. (Item 46) Item 34. The method of item 33, further comprising generating the optical carrier using the optical network element. (Item 47) 34. The method of claim 33, further comprising modulating digital diagnostic data onto the optical carrier. (Item 48) Item 48. The method of item 47, wherein the digital diagnostic data includes at least one of a hardware identification number, optical channel monitor calibration data, optical network element calibration data, and optical element alarm threshold data. (Item 49) 1. A method of configuring an optical network element in a hardware configured optical network, the method comprising: a) receiving an optical signal from the hardware-configured optical network, the optical signal including receive control information; b) demodulating the received control information from the hardware configured optical network; and c) detecting an error condition within the hardware-configured optical network from the demodulated received control information; and d) generating transmission control information including configuration information for correcting the error condition within the hardware configured optical network; and e) modulating transmission control information onto an optical carrier to thereby generate a transmission optical control signal representative of said transmission control information including configuration information for correcting said error condition within said hardware configured optical network; f) transmitting, on said optical carrier, said transmission optical control signal representing said transmission control information including configuration information for correcting said error condition in said hardware-configured optical network to said hardware-configured network; A method comprising: (Item 50) a) receiving, at a second optical network element, the transmit optical control signal including configuration information for correcting the error condition in the hardware configured optical network; b) at a second optical network element, demodulating the received control information, the control information including configuration information for correcting the error condition; and c) reconfiguring the second optical network element in accordance with the demodulated received control information configuration information that corrects the error condition, thereby correcting the error condition in the hardware configured optical network. 50. The method of claim 49, further comprising: (Item 51) 50. The method of claim 49, wherein the error condition in the hardware configured optical network includes a wiring error. One aspect of the present teachings is that the hardware configured network described herein can provide digital diagnostics for optical network elements. Known transceivers sometimes include a microprocessor and a diagnostic interface that provides performance information over a data link. This allows a user to remotely monitor in real time a number of performance parameters, such as received optical power, transmitted optical power, laser bias current, transceiver input voltage, and transceiver temperature, of any transceiver in the network. The digital diagnostics capability provides users, clients, and external network management systems with the tools to implement performance monitoring.

[0007] The present teachings, according to preferred and exemplary embodiments, together with further advantages thereof, are more particularly described in the following detailed description taken 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, emphasis instead generally being placed on illustrating the principles of the present teachings. In the drawings, like reference characters generally refer to like features and structural elements throughout the various views. The drawings are not intended to limit the scope of the applicant's teachings in any way. [Brief description of the drawings]

[0008] [Figure 1A] FIG. 1A illustrates a block diagram of an embodiment of a hardware configuration optical element of the present teachings. [Figure 1B]FIG. 1B illustrates a block diagram of an embodiment of a hardware configured optical element of the present teachings in which an optical carrier signal is generated internally within the optical element. [Figure 1C] FIG. 1C illustrates a block diagram of an embodiment of a hardware configuration optical element of the present teachings in which an optical carrier signal originates from an optical network. [Figure 1D] FIG. 1D illustrates a block diagram of one embodiment of a hardware configuration optical element comprising an optical transceiver. [Figure 1E] FIG. 1E illustrates an oscilloscope trace of the measured output of the optical transceiver described in connection with FIG. 1D on a transmission fiber. [Figure 2A] FIG. 2A illustrates a block diagram of one embodiment of a hardware configuration optical element comprising an optical transceiver with a tunable transmitter. [Figure 2B] FIG. 2B illustrates an optical spectrum representing the measured output of a tunable transceiver on a transmission fiber in accordance with the present teachings. [Figure 3A] FIG. 3A illustrates a hardware configured network element in accordance with the present teachings, including a wavelength selective switch. [Figure 3B] FIG. 3B shows an oscilloscope trace of the measured output of a wavelength selective switch illustrating a low frequency control signal in accordance with the present teachings. [Figure 4] FIG. 4 illustrates a block diagram of one embodiment of a hardware configuration optical element including an optical amplifier in accordance with the present teachings. [Diagram 5] FIG. 5 illustrates an oscilloscope trace of a low frequency control signal in accordance with the present teachings, including a collision avoidance protocol based on modifications to the well-known Ethernet protocol. [Figure 6] FIG. 6 illustrates an embodiment of a hardware configured network of the present teachings in a point-to-point transceiver topology, also referred to in the art as an optical link. [Figure 7] FIG. 7 illustrates an embodiment of a hardware configured network of the present teachings comprising multiple tunable transceivers connected to wavelength selective switches or optically programmable filter elements. [Figure 8] FIG. 8 illustrates an embodiment of a hardware configured network of the present teachings that includes a wavelength division multiplexing network with wavelength selective switching optical elements. [Figure 9] FIG. 9 illustrates the hardware configuration network of FIG. 8 with the wiring incorrectly installed. [Figure 10] FIG. 10 illustrates an embodiment of the hardware configured WDM network of FIG. 8 in which the installer miswired the elements at location A. [Figure 11] FIG. 11 illustrates an embodiment of a low-cost combiner-splitter incorporating hardware components according to the present teachings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] As used herein, a reference to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the present teachings. The appearances of the phrase "in one embodiment" in various places in the specification do not necessarily all refer to the same embodiment.

[0010] It should be understood that the individual steps of the methods of the present teachings can be performed in any order and / or simultaneously so long as the present teachings remain operable. Further, it should be understood that the apparatus and methods of the present teachings can include any number or all of the described embodiments so long as the present teachings remain operable.

[0011] The present teachings will now be described in more detail with reference to exemplary embodiments thereof as illustrated in the accompanying drawings. While the present teachings are described in conjunction with various embodiments and examples, it is not intended to limit the present teachings to such embodiments. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be understood by those skilled in the art. Those skilled in the art with access to the present teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, that are within the scope of the present disclosure described herein.

[0012] The term "element" or "network element" is used herein to describe various devices and optical subsystems used to build and operate an optical network. Some examples of these are transceivers, switches, wavelength selective switches, programmable filters, amplifiers, add-drop multiplexers, and cross-connect equipment. The term "component" as used herein describes the optical, mechanical, and electronic components that make up these subsystems. The term "network" describes multiple network elements connected to form a group or system of elements that operate to exchange information and cooperate.

[0013] In this disclosure, when used in connection with a network, the terms "configure," "configuring," and "configure" are meant to include various network management, control, and operation functions. For example, the term "configure" includes tasks such as element audit, element diagnostics, element performance monitoring, and control of element operating parameters. Some terms in the art that should be considered part of the definition of "configure" include network management, network operation, FCAPS (Fault Management, Configuration, Accounting, Performance, Security), and network monitoring and alerting. Network management includes tasks such as configuring, discovering, identifying, and auditing network elements, discovering and reacting to failures or misconfigurations of network elements, and monitoring the performance of network elements. In addition, the term "configure" can apply to a single element, or it can apply to a collection of elements that operate, or are intended to operate, as a connected system or network. In particular, the term "configuring a network" includes tasks such as network discovery, passive monitoring of network operation, and active control.

[0014] Modern optical network elements are generally configured via optical client interfaces. Little or no management information is exchanged directly between elements such as transceivers, wavelength selective switches, amplifiers, and other elements in the optical network. Configuration information is typically transmitted on a single channel, which limits the amount of management information and the number of network elements that can be configured. The single management or monitoring channel also limits the amount of information available to external network management systems, especially during calibration operations.

[0015] Furthermore, in modern optical network configuration systems, large amounts of diagnostic information are transmitted from the network elements to one or more external network management systems or users for processing. The diagnostic information is processed within the external network management systems and instructions are subsequently sent back to the elements to generate 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 especially true as the amount of information required to be processed from the network elements increases to improve element monitoring and / or provide dynamic element operation. For example, support for dynamic traffic routing requires optical elements that provide a significant amount of real-time data for optical path calculations, including in-line amplifier performance and dynamic path spectrum conditions.

[0016] It would therefore be highly desirable to have a method and apparatus for configuring elements in an optical network that is automated, tunable across multiple channels, and functional across the various optical elements that make up the network. The present teachings relate, at least in part, to methods and apparatus for transmitting and processing control and management information for a hardware configured network (HCN). The term "hardware configured network," as used herein, is a networked system of optical and electrical switching and transport elements and components that automatically configure, control, and manage their operation with little or no user input.

[0017] One possible characteristic of a hardware configuration network is that it automatically connects and provisions channels and wavelengths without centralized commands or user intervention. Another possible characteristic of a hardware configuration network is that it detects and corrects configuration errors without centralized commands or user intervention. Yet another possible characteristic of a typical hardware configuration network is that it reconfigures optical elements without centralized commands or user intervention. Examples of configurations performed by a hardware configuration network include element adjustments, tuning of wavelength tunable elements, programming programmable optical filter characteristics (such as bandwidth, filter shape, dispersion, and other configurable parameters), setting attenuation levels of wavelength selective switches (WSS), setting gain and gain spectrum in erbium doped fiber amplifiers (EDFA), and configuring ports and wavelengths per port for optical switches and wavelength add-drop multiplexers and cross-connect devices. Although the hardware configured network aspects of the present teachings are described in connection with self-configuration of network elements, those skilled in the art will understand that user and / or centralized command or external management systems with access to hardware configured network information and configuration control may also be used in conjunction with self-configuration of network elements.

[0018] FIG. 1A illustrates a block diagram of an embodiment of a hardware-configured optical element according to the present teachings. Instead of using a dedicated supervisory optical channel, the hardware-configured network of the present teachings transmits control information through the network using low-frequency modulation modulated on various optical signals traversing the network. That is, the optical carrier for the low-frequency modulation used to transmit and receive control information is part of the optical signal propagating within the network. These optical signals used as optical carriers in various embodiments of the hardware-configured network of the present teachings can include client data traffic, dummy signals, CW light, and spontaneous emission amplified light. The term "optical carrier" as used herein is defined as any light that is modulated (which may be low-frequency modulated). 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 a particular wavelength of light, often an ITU grid-based wavelength, that is used to carry data from a laser transmitter. In various embodiments, the optical carrier can be generated within the optical element itself or can be an optical carrier received from the network.

[0019] The hardware configurable optical element 100 includes an electronic control port 102 for transmitting and receiving electrical control information. The hardware configurable optical element 100 also includes an output port coupled to a transmit optical fiber 104 for transmitting an optical signal to an optical network, and an input port coupled to a receive optical fiber 106 for receiving from the optical network. A demodulator 108 decodes the received control information and transmits the decoded control information to a control processor 110, which processes the information and configures the optical element according to the control information.

[0020] The optical modulator 112 modulates an optical carrier with the transmission control information so that the transmission control information can be transmitted into the optical network. In one method of operation, the optical modulator 112 modulates the optical carrier with a low frequency modulation signal that represents the transmission control information. The transmit optical control signal is then transmitted to the network using the transmission fiber 104. In some methods of operation, the transmit optical control signal is directly applied to a client data signal that serves as the optical carrier, and this combination of modulated optical signals is then transmitted on the transmission fiber 104.

[0021] FIG. 1B illustrates a block diagram of an embodiment of a hardware configuration optical element 120 of the present teachings, where an optical carrier signal is generated by an optical signal generator 122 inside the optical element. In some embodiments, the optical signal generator 122 is part of a client transmitter of the optical transceiver element. In some embodiments, the optical signal generator 122 includes an optical amplifier, and the optical carrier is amplified spontaneous emission light. A modulator 124 is used to modulate the optical carrier with control information. In some methods of operation, the control information is generated by a local processor 126. In other methods of operation, the control information is generated by a remote source having an output electrically connected to an electronic control port 128. A splitter 130 is used to separate the portion of the input optical signal that includes the received control signal from the optical network 132. A demodulator 134 decodes the received control information and then transmits the received control information to the control processor 126, which configures the hardware component 120 based on the provided control information.

[0022] 1C illustrates a block diagram of an embodiment of a hardware configuration optical element 140 of the present teachings, where an optical carrier signal originates outside the optical element. The optical carrier originates from an optical network and arrives at an input fiber 142. A portion of the optical signal from the input fiber 142 is split off and sent to a demodulator 148. The demodulator 148 decodes the received control information and then sends the received control information to a control processor 149, which configures the hardware component 140 based on the provided control information. A portion of the optical signal is split off by a splitter 144 and sent to an optical modulator 146, which provides the transmitted control information to the optical carrier in the form of low frequency modulation. The transmitted optical control signal then exits the optical element on a transmission fiber 147.

[0023] In some embodiments, the optical carrier comprises a client data signal generated by an optical transceiver element upstream of the hardware configuration optical element 140. In other embodiments, the optical carrier comprises amplified spontaneous emission light from an upstream optical amplifier. FIG. 1D illustrates a block diagram of one embodiment of a hardware configuration optical element comprising an optical transceiver 150. The optical transceiver 150 includes an electrical control port 152 for transmitting and receiving electronic command and control information. In some embodiments, the electrical control port 152 is an industry standard I2C interface. In other embodiments, the electrical control port 152 uses a multi-master, multi-slave, serial protocol used for built-in system control. The optical transceiver 150 also includes an output that is optically coupled for transmission to an optical fiber 154, and an input that is optically coupled to a receiving optical fiber 156 that carries the optical signal to the optical transceiver 150. In both the transmitting and receiving optical fibers, the optical signal can include one or both of the client data traffic as well as low frequency control signals. The client data traffic can include network traffic being transmitted across the network. The low frequency control signals can include various types of information used to configure the network element.

[0024] Figure 1E illustrates an oscilloscope trace of the measured output 160 of the optical transceiver 150 described in connection with Figure 1D on a transmission fiber 154. With reference to both Figures 1D and 1E, in this embodiment, the optical transceiver 150 generates client data traffic 162 at a 10 Gb / s data rate. The client data traffic 162 appears as high and low data levels as a function of time on a relatively long time scale.

[0025] Thus, one aspect of the present teachings is to encode the control signal 164 using a series of "1's" and "0's" at a low frequency that is applied directly to the optical communication signal originating from the transceiver 100. In the embodiment shown in Figures 1D, 1E, 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's" and "0's" can be decoded in a corresponding receiving optical element (not shown) that is optically coupled to the transmission fiber 154. The low frequency modulation can be amplitude modulation, as shown in Figure 1E. In various other embodiments, the low frequency modulation can be any modulation format, such as phase modulation or frequency modulation.

[0026] It is important to note that the client data traffic 162 is not affected by the low frequency modulation. One advantage of encoding the control signals using a series of "1's" and "0's" at a low frequency 164 directly applied to the optical signal originating from the transceiver 150 is that the frequency used for the low frequency modulation does not pass through the electrical filters in the receiver that typically decode the high data rate of the client data traffic 162. Depending on the details of the modulation, scrambling, and coding of the optical signal, the baseline wander may set the low frequency cutoff of these high pass electrical filters as low as 100 kHz. As a result, the frequency of the low frequency control signals is selected to be below the lowest frequency of the high pass filtering used in the transceiver, and thus the low frequency control signals will not affect the integrity of the client data traffic 162. Furthermore, low frequency modulation based encoding and decoding can be accomplished using relatively low cost and low bandwidth optical and electronic equipment that is well known and widely available in the art. Some embodiments of a hardware configured network according to the present teachings use optical and electrical components already available in currently deployed transceiver 150 elements.

[0027] 2A illustrates a block diagram 200 of one embodiment of a hardware configuration optical element comprising an optical transceiver with a tunable transmitter 202. The tunable transmitter 202 includes an electrical control port 204 for transmitting and receiving command and control information. 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 used for on-board system control. The tunable transceiver 202 includes an output that is optically coupled to a transmission fiber 206.

[0028] 2B illustrates an optical spectrum 208 representing the measured output of a tunable transceiver on a transmission fiber 206 in accordance with the present teachings. The optical spectrum 208 shows that a tunable laser in the tunable transceiver 202 is set to a particular wavelength 210. In one particular embodiment, the wavelength or channel of the tunable transceiver 202 can be set and tuned over a wavelength range of 1528 nm to 1567 nm.

[0029] 2A and 2B, in this embodiment, the optical transceiver 200 is generating client data traffic 224 at a 10 Gb / s data rate, shown as high and low data levels as a function of time with a relatively long time scale in the oscilloscope trace. Control and management information for configuring the network is encoded as a series of "1's" and "0's" 222 at low frequency that is directly fed to the client data traffic 224. In some methods of operation according to the present teachings, a typical output power for the tunable transceiver 202 is in the range of 0-3 dbm, which corresponds to approximately 1-2 mW. Furthermore, in some methods of operation, the low frequency encoded modulation format is a low frequency power variation of the tunable laser channel, thus operating at the wavelength of the laser channel set point. Additionally, in some methods of operation, the modulation depth of the low frequency modulation is approximately 0.5%-10%. In some embodiments, the low frequency modulation is 5% or less.

[0030] Thus, one feature of the hardware-configured network according to the present teachings is that the control information is encoded on the tunable transmitter signal, and thus the wavelength carrying the encoded control information is tunable based on the tunable configuration of the tunable transmitter. As a result, by adjusting the wavelength of the signal carrying the encoded information, the destination of the encoded control information can be changed based on the particular wavelength path configured within the optical network. For example, the configuration of wavelength switches, filters, and amplifiers that make up the optical network establishes wavelength paths from sources to destinations within the optical network. The wavelength paths from various sources to various destinations can also change based on reconfiguration of the network elements. The source wavelength can be adjusted to follow a desired wavelength path to a particular destination or set of destinations, and thus a low-frequency control signal provided to an optical signal at that source wavelength will provide the encoded control information to that particular destination or set of destinations. The destination of the low-frequency control signal can therefore be changed simply by adjusting the laser wavelength of the tunable transceiver. This ability to select wavelengths that carry low frequency modulated control signals allows encoded control information from one network element to potentially reach any of a variety of different elements within the network by selecting a particular wavelength path.

[0031] Another feature of a hardware configured network according to the present teachings is that the low frequency encoding of control signals on a particular wavelength does not affect other wavelengths propagating within the optical fiber or the overall optical network.

[0032] FIG. 3A illustrates a hardware-configured optical element 300 according to the present teachings, including a wavelength selective switch 302. 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 are widely available in a variety of port configurations and channel plans and are currently used in modern optical networks. Wavelength selective switches, such as those manufactured by Finisar Corporation, provide a highly programmable and flexible switching platform for switching traffic from one optical link to another across multiple wavelengths within the same network. However, a wavelength selective switch according to the present teachings can be constructed with additional features in accordance with 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 the encoded control data.

[0033] Moreover, the wavelength selective switches used in the hardware configured network according to the present teachings are bidirectional and can operate equally in both directions. Thus, one aspect of the present teachings is that the wavelength selective switch 302 can also receive and decode control signals from other optical elements in the network, and transmit and encode control signals intended for other optical elements in the network.

[0034] The hardware configuration optical element 300 includes a wavelength selective switch 302 with at least one optical input optically connected to a receive optical fiber 304 and a plurality of optical outputs optically connected to a plurality of transmit optical fibers 306, 306', 306''. The wavelength selective switch 302 also has an electrical control port 308. In some operational methods according to the present teachings, the receive optical fiber 304 propagates an optical signal on one or more wavelengths. Referring back to FIGS. 2A and 2B, the optical signal may include client data traffic originating from the tunable optical transceiver 202.

[0035] 3A illustrates client data traffic 310 on a receive fiber 304. One function typically performed by a wavelength selective switch 302 is to vary the attenuation of a received optical signal in response to an electronic control signal and generate an amplitude modulated signal from the varying attenuation. The result is a low frequency modulation performed on the optical signal received on the optical input of the wavelength selective switch 302, which can be independently imparted to optical signals at any or all wavelengths or channels passing through the wavelength selective switch 302.

[0036] 3A also illustrates client data traffic 310 accompanied by low frequency control signals 312 in the form of a series of "1's" and "0's" encoded by the electronic control signals. Note that the integrity of the client data traffic 310 is not affected by the low frequency control signals. The low frequency control signals are selectively applied to desired wavelength channels that are routed to one of the multiple transmission fibers 306, 306', 306'' using electronic control signals that selectively control the attenuation of particular wavelength channels in the wavelength selective switch 302.

[0037] The low frequency control signal in the form of a series 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, as shown in the oscilloscope trace 350 illustrated in FIG. 3B. FIG. 3B shows an oscilloscope trace 350 of the measured output of the wavelength selective switch 302 on the receiving fiber 306, where the client data traffic has been filtered in accordance with the present teachings. The result is a first signal level for the "1's" resulting from low attenuation through the wavelength selective switch 302, and a second, lower signal level for the "0's" resulting from higher attenuation through the wavelength selective switch 302. The data rate for the filtered control signal can be relatively low. For example, the data rate of the low frequency control signal can be about 5 bits / second.

[0038] FIG. 4 illustrates a block diagram of one embodiment of a hardware-configured optical amplifier 400. In the embodiment shown, the hardware-configured optical amplifier 400 is an erbium-doped fiber amplifier (EDFA), which is an optical amplifier commonly used in modern optical communication systems. Those skilled in the art will appreciate that numerous other types of optical amplifiers can also be used. The optical amplifier 400 includes an electrical control port 402 configured for transmitting and receiving electrical command and control information. The optical amplifier 400 also includes an optical input port coupled to a receiving optical fiber 404 that provides the optical signal to be amplified, and an optical output port coupled to a transmitting optical fiber 406 that transmits an amplified optical signal that may also include a low-frequency control signal in accordance with the present teachings.

[0039] 4 also illustrates an oscilloscope trace of incoming client data traffic 408 provided by a receiving fiber 404 to be amplified by the optical amplifier 400. In this embodiment, the client data traffic 408 is modulated at, for example, a 10 Gb / s data rate. The optical amplifier 400 varies the attenuation of the received optical signal and generates a low frequency amplitude modulated control signal 410.

[0040] In the embodiment shown in Figure 4, the configuration information is encoded on a low frequency modulated control signal using electronic control signals provided by the control port 402. The configuration information data in the low frequency amplitude modulated control signal 410 is encoded as a series of "1's" and "0's" using low frequency modulation applied to the client data traffic 408 as shown in Figure 4. The integrity of the client data traffic 408 is not affected by the low frequency amplitude modulated control signal because the amplitude modulation depth of the low frequency modulation is small relative to the modulation depth of the client data traffic. In addition, the integrity of the client data traffic 408 is not affected by the low frequency amplitude modulated control signal because the frequency of the low frequency modulation is too low to pass the receive filter of the client data traffic.

[0041] As described herein, one feature of the hardware configured network of the present teachings is that the integrity of the client data traffic 408 is not affected by the small amount of low frequency modulation provided by the optical amplifier 400. In some embodiments, the amplitude modulation provided by the optical amplifier 400 provides low frequency modulation across the entire spectral bandwidth of the 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 the optical amplifier 400 receive the same encoded information from the electronic control signal. However, in other embodiments of the present teachings, the optical amplifier 400 has a gain control capable of controlling the gain for a particular channel or band of channels passing through the optical amplifier 400. In these embodiments, the control signal is encoded on selected ones of one or more channels, wavelengths, or bands passing through the optical amplifier 400.

[0042] One feature of the present teachings is that the low frequency control signal can be provided to various types of existing optical signals. For the embodiments illustrated in connection with Figures 1D-1E and 2, the existing optical signal includes client data traffic originating from the transceiver elements. In some embodiments, the existing optical signal does not include live data traffic. For example, the existing optical signal may include a dummy communication data signal. In other embodiments, the existing optical signal includes a CW output of an optical transceiver or amplified spontaneous emission light from an optical amplifier.

[0043] Further, in some embodiments, the existing optical signal originates from the same optical element that provides the electronic control information to the existing optical signal. In other embodiments, the existing optical signal originates from another optical element upstream of the optical element that provides the electronic control information to the existing optical signal. In some embodiments, electronic control information from one or more separate elements connected in the network is provided 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 within the optical network element provides configuration information for the optical control signal. In some embodiments, the configuration information for the transmit optical control signal provided by the processor within the optical network element is generated based on the received optical control signal.

[0044] In one embodiment of the present teachings, the hardware configuration optical elements include a counter-propagating Raman pump unit and a variable gain (VG) optical amplifier, such as a variable gain EDFA optical amplifier. The Raman pump unit and the variable gain optical amplifier can be integrated to provide very low noise figure and excellent gain flatness, which are highly desirable characteristics for ultra-long-haul optical communication systems. Modern optical amplifier modules can currently support up to three Raman / EDFA pump optical amplifiers in various configurations.

[0045] In embodiments using Raman pump units and variable gain optical amplifiers, a fast automatic gain control (AGC) circuit can be used to provide advanced transient suppression that allows the optical amplifier to maintain constant gain during operating conditions in the presence of fast and large changes in input power independent of the stimulated emission amplified light (ASE) generated by the Raman pump optical amplifier. A suitable variable gain dual stage erbium doped fiber amplifier that provides flat gain across the C-band with a low noise figure and wide dynamic gain range (up to 15 dB) is commercially available from Finisar Corporation. In some embodiments, the optical amplifier includes features such as comprehensive transient control, wavelength tunable interstage access (MSA) loss, and gain tilt functionality, all of which can be used together or separately to control attenuation through the device for performing low frequency modulation on an existing optical signal.

[0046] One feature of the present teachings is that a hardware configured optical element provides a means for transmitting configuration information to elements in a network that includes multiple hardware configured optical elements. The method and apparatus of the present teachings are compatible with existing and deployed optical elements 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 datacom and telecom networks, such as large service provider networks and enterprise networks; as well as private networks and ad-hoc 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 elements in a point-to-point manner. In other embodiments, configuration information is exchanged between optical elements in a broadcast or multicast manner to some or all of the optical elements on the network. In still other embodiments, configuration information is exchanged in a multipoint or cascaded manner. In various embodiments, any combination of these means for exchanging configuration or control signal information between optical elements can be used.

[0047] Another feature of hardware configured networks comprising hardware configured optical elements of the present teachings is that known communication protocols and known management information protocols may be used to configure the network elements. That is, known systems of rules for gathering information from and configuring the network elements may be used. These protocols include, for example, data communications, telecommunications transport, and management protocols used to manage 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 system, real-time system, and computer bus protocols.

[0048] FIG. 5 illustrates an oscilloscope trace of a low-frequency control signal 500 according to the present teachings, which includes a collision avoidance protocol based on a modification to the well-known Ethernet protocol. The low-frequency control signal 500 shown in FIG. 5 includes a protocol suitable for multipoint communication. The encoded control information is transmitted in "bursts", shown as regions 502, 502', and modulated "1's" and "0's" appear on the client data traffic 504. The burst duration, shown as time t 506, is short compared to the retransmission time T 508. In some embodiments, the ratio of t / T is 0.1, such that the packet time is only 10% of the retransmission time. Each transceiver utilizes a random percentage of the retransmission time for the packet bursts to avoid potential collisions of packets transmitted from different transmitters and improve the reliability of decoding at the receiver. In other words, t / T for the various transmitters are randomly selected.

[0049] One aspect of the present teachings is that the optical elements in a hardware configured network can be arranged in any network configuration, including mesh, point-to-point, ring, bus, tree, and other known configurations. Furthermore, the optical elements of a hardware configured network of the present teachings can include several different element types, including transceivers, amplifiers, optical channel monitors (OCMs), wavelength selective switches, WDM multiplexers and demultiplexers, cross-connect devices, and optical switches. Thus, the configuration system of the present teachings supports a multitude of network topologies, network sizes and scopes, and network services.

[0050] Another aspect of the present teachings is that a heterogeneous combination of optical network elements, including transceivers, amplifiers, optical channel monitors, wavelength selective switches, multiplexers / demultiplexers, cross-connect devices, and optical switches, can be configured using a common configuration scheme as described herein.

[0051] FIG. 6 illustrates an embodiment of a hardware-configured network of the present teachings in a point-to-point transceiver topology, also referred to in the art as an optical link. The point-to-point configuration shown in FIG. 6 can also be extended to other more complex network topologies including additional optical transceiver elements such as mesh, ring, and bus. In the embodiment illustrated in FIG. 6, two optical transceivers 602, 602' are connected via one optical fiber 604 for transmitting 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.

[0052] The transceiver 602 includes control ports 608, 608' for transmitting and receiving command and control information signals. An oscilloscope trace 609 of the measured output of the first transceiver 602 shows normal client data traffic 610 at a 10 Gb / s data rate, and a low frequency control signal 612. Note that the integrity of the client data traffic 610 is not affected by the low frequency control signal 612. The low frequency control signal 612 shown in FIG. 6 is an amplitude modulated signal, but one skilled in the art will understand that any modulation format can be used. The low frequency control signal 612 contains the control and management information transmitted from the first transceiver 602. A microprocessor in the second optical transceiver 602' is used to decode the series of "1's" and "0's" received from the first optical transceiver 602. In this manner, configuration information is shared from the first optical transceiver 602 to the second optical transceiver 602'.

[0053] The second optical fiber 606 is used to transmit configuration information from the second transceiver 602' to the first transceiver 602. In this manner, the 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' may include an industry standard I2C interface or other type of communication interface. Thus, using the low frequency modulation method of the present teachings, digital diagnostic information can be encoded, shared, and decoded in both directions between the two transceivers 602, 602'.

[0054] FIG. 7 illustrates an embodiment of a hardware configured network 700 of the present teachings, comprising multiple tunable optical transceivers 702, 702′ connected to a wavelength selective switch or optically programmable filter element 704. Wavelength selective switches can be used to route optical signals between optical fibers based on a particular wavelength or channel. Wavelength selective switches can be configured as reconfigurable optical add-drop multiplexers and act as automated patch panels to rapidly shift wavelengths and bandwidths to different fibers. For example, Flexgrid 1000 series switches available from Finisar Corporation can be used to route optical signals between optical fibers based on a particular wavelength or channel. TM The technology product provides dynamic control of channel center frequency with 6.25 GHz resolution and 12.5 GHz channel width resolution in a wavelength selective switch. TM Once deployed with the technology, channel plans are configurable "on the fly," meaning that channel bandwidths can be adjusted to most efficiently carry future demands as they arise, or for any other purpose.

[0055] An example of a modern programmable optical filter is the WaveShaper family of programmable optical processors available from Finisar corporation.

[0056] Programmable optical filters offer a variety 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 functions such as tunable optical filtering, optical bandwidth management, dynamic gain equalization, programmable optical filtering, polarization handling, and multi-port optical handling. All these parameters of the wavelength selective switches and programmable optical filters can be configured using the hardware configuration network methods and apparatus of the present teachings.

[0057] 7 illustrates two optical transceivers 702, 702' with optical outputs connected to inputs of a programmable filter element 704 using optical fibers 706, 706'. The optical connections between the two transceivers 702, 702' and the programmable filter element 704 are bidirectional in many configurations. The programmable filter 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, 702' have electronic control ports 712, 714 for receiving electronic control signals.

[0058] In some embodiments, the optical transceivers 702, 702' are tunable and configured to transmit and receive different wavelength channels. In the configuration shown in Figure 7, the programmable filter element 704 is programmed to receive two wavelength channels and transmit them on the output fiber 708. Those skilled in the art will appreciate that any number of transceivers with any number of channels can be used with the methods and apparatus of the present teachings.

[0059] In some embodiments, a local client 716 is used to provide control information for configuring the programmable filter elements 704 and for setting the wavelength channels from the transceivers 702, 702'. In some embodiments, the control information is provided independently from an external source using the control ports 710, 712, and 714. The control information is encoded on low frequency control signals that are applied to existing optical signals propagating on the optical fibers 706, 706', and 708. In this manner, information for element configuration is transferred throughout the network. Both local client based and independent input methods are used in some embodiments. In various embodiments, the local client may or may not be co-located with the optical elements.

[0060] FIG. 8 illustrates an embodiment of a hardware-configured network 800 of the present teachings that includes a wavelength division multiplexed network with wavelength-selectively switched optical elements. Many known network element configurations rely on the use of clients to communicate configuration information to various elements in the wavelength division multiplexed network using a separate "supervisory" channel. One feature of the hardware-configured network of the present teachings is that known client hardware is no longer required to provide element configuration. While client hardware and other external management systems can be present and used in the network, they are no longer required for element configuration. Furthermore, if these client hardware and other external management systems are used, they may have a greatly reduced role. Instead, configuration information is provided via low-frequency control signals applied to existing optical signals in the optical network, as described herein.

[0061] 8 illustrates first and second transceivers 802, 802' having bidirectional optical ports that are optically coupled to an add wavelength selective switch 804 using optical fibers 806, 806'. In some embodiments, there is bidirectional communication between the first and second transceivers 802, 802' and the add wavelength selective switch 804. In other embodiments, there is only unidirectional communication from the first and second transceivers 802, 802' to the add wavelength selective switch 804. The transceivers 802, 802' include control ports 808, 808' that receive control information.

[0062] The add wavelength selective switch 804 has an electrical control port 810 that receives control information. In some embodiments, the electrical control port 810 is not used and the control information is provided via optical fibers 806, 806'. In addition, the add wavelength selective switch 804 includes an optical bidirectional port that is optically coupled to a bidirectional port of a drop wavelength selective switch 814 using an optical fiber 812. The drop wavelength selective switch 814 has an electrical control port 816 that receives control information. In operation, the add wavelength selective switch 804 can be configured to connect various wavelengths from various input ports to specific output ports in a controllable manner. The drop wavelength selective switch 814 can also be configured to connect various wavelengths from specific input ports to one or more of the various output ports in a controllable manner. Those skilled in the art will appreciate that the add wavelength selective switch 804 and the drop wavelength selective switch 814 can also operate in the opposite direction, such that the add wavelength selective switch 804 is a drop wavelength selective switch and vice versa.

[0063] The drop wavelength selective switch 814 also includes two bidirectional ports optically coupled to first and second optical fibers 818, 818'. In the embodiment shown, the optical fibers 818, 818' transmit optical signals from the drop wavelength selective switch 814 to the transceivers 820, 820'. The transceivers 820, 820' have electrical control ports 822, 822'. In the embodiment shown in Figure 8, the transceivers 802, 802' transmit signals from the add wavelength selective switch 804 through the drop wavelength selective switch 814 to the receiving transceivers 820, 820'.

[0064] 8, a transceiver 802 at location A 824 is in a transmit mode and is optically coupled to a transceiver 820 at location B 826 in a receive mode. Similarly, a transceiver 802' at location A 824 is in a transmit mode and is connected to a transceiver 820' at location B 826, which is in a receive mode. In one method of operation, the transceiver 802 is configured, at least in part, using a client configuration device 828 to provide data on a particular wavelength channel.

[0065] The encoded control information is provided using low frequency modulation on the wavelength channels originating from the transceiver 802 that are sent to the add wavelength selective switch 804. The encoded control information is received by the add wavelength selective switch 804, then decoded and used to configure the add wavelength selective switch 804 to pass the signal from the transceiver 802 to an output fiber 812 that is connected to the drop wavelength selective switch 814. This action causes the control signal to be passed to the drop wavelength selective switch 814, where it is subsequently decoded. The drop wavelength selective switch 814 then uses the decoded control information to configure the drop wavelength selective switch 814 to pass the signal from the transceiver 802 to a fiber 818. This configuration of the drop wavelength selective switch 814 thereby passes the signal originating from the transceiver 802 and the encoded control information to the receiver 820. The encoded control information is received at the transceiver 820, where it is used to configure the transceiver 820 to receive the signal data from the transceiver 802.

[0066] In some embodiments, one or more optical channel monitors 830, 832 provide control information to the hardware configurable add and drop wavelength switches 804, 814. The optical channel monitors 830, 832 monitor details of the optical signals passing through the add wavelength selective switch 804 or the drop wavelength selective switch 814, or both, and use that information to inform various control actions of the hardware configured network. The control actions are signaled to the network via low frequency modulation as described herein.

[0067] Those skilled in the art will appreciate that the add wavelength selective switch 804 and the drop wavelength selective switch 814 are capable of simultaneously running traffic in both the forward and reverse directions, however, two optical fibers between each element are required to carry traffic in both directions.

[0068] Those skilled in the art will appreciate that the particular sequence of events illustrating the automated configuration and provisioning use of a hardware configuration network shown in FIG. 8 is illustrative and not limiting of the present teachings in any way. For example, various protocols can be used to establish network connectivity and network configuration between optical elements in various sequences using the low frequency control signals described herein. Furthermore, a client can be used to provide electronic control signals to any of the elements in the network for any or all of the configuration events. In addition, a client can be used to initiate one or more configuration events, and automated encoded information is used for the remainder of the configuration events.

[0069] One aspect of the present teachings is that installation errors can be detected in an automated manner without the use of a client or an external network manager. Installation errors cause the actual deployed hardware physical connections to deviate from the planned hardware physical connections. The term "physical connections" as used herein refers to the connection of a specific port of one or more optical elements to a specific fiber or specific port on the optical element. When installation errors occur, the planned element configurations that are preprogrammed into the optical elements inferring the planned hardware physical connections will not result in proper optical signal paths between the elements. In known configuration systems, the only way to recover from installation errors is to use expensive human intervention to both detect the erroneous connections and redeploy the hardware and establish the planned hardware physical connections.

[0070] FIG. 9 illustrates the hardware configuration network 900 of FIG. 8, where an installation error occurs at location B. 9, causing a cross-wire condition at 902. The planned wiring connection calls for 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 results in receiving transceiver RX-1 904 being connected to optical fiber 910 and receiving transceiver RX-2 908 being connected to optical fiber 906 as shown in FIG. 9. Such installation errors are unfortunately a common occurrence for telecommunications service providers, causing significant service build-up delays and additional costs. Cross-wire conditions are difficult to detect and difficult to correct, even with modern network hardware configuration systems. Detection of an installation error condition requires correlation of error conditions from multiple network elements using a human operator, and subsequent service requires a field technician to locate and reconnect the equipment to the planned physical connections.

[0071] Using the hardware configuration network apparatus and method of the present teachings, the cross-wiring installation error of Figure 9 can be automatically detected and corrected with virtually no human intervention or truck roll. Specifically, upon start-up, the drop wavelength selective switch 912 transmits an optical signal including a low frequency control signal in accordance with the present teachings from the transmitting transceiver TX-1 916 at Location A 914 to the receiving transceiver RX-2 908 at Location B 902. The receiving transceiver RX-2 908 at Location B 902 identifies a connection error because the configuration information encoded on the low frequency control signal is from TX-1 916 at Location A 914 and not from TX-2 918 at Location A 914 as would be expected. The receiving transceiver RX-2 908 at Location B 902 then initiates a corrective action by encoding corrective configuration information on the low frequency control signal that is directed to the appropriate network element to provide a corrective action to eliminate the installation error.

[0072] In particular, the wiring errors are corrected using a reconfiguration of the drop wavelength selective switch 912. The reconfiguration is initiated by encoded information sent from the receiving transceiver RX-2 908 at Location B 902 to the drop wavelength selective switch 912 at Location B 902 to reconfigure the drop channels such that RX-2 908 at Location B 902 receives optical signals from TX-2 918 at Location A 914. Thus, the drop wavelength selective switch 912 is reconfigured based on control information sent from the receiving transceiver RX-2 908 such that the signal from TX-1 916 at Location A 914 occurs on the deployed fiber 910 instead of the planned fiber 906, and the signal from TX-2 918 at Location A 914 occurs on the deployed fiber 906 instead of the planned fiber 908. In this manner, the reconfiguration of optical elements in a hardware configured network of the present teachings corrects installation errors without expensive human intervention. Extensions to other installation errors and the necessary reconfiguration steps are well understood by those skilled in the state of the art of network configuration and disaster recovery.

[0073] One aspect of the present teachings is the ability to catch installation errors early on at the transmit side of the network, rather than detecting configuration errors only when the signal reaches the receive side of the network, as is currently done in known systems. Figure 10 illustrates an embodiment of the hardware configured wavelength division multiplexing network 1000 of Figure 8, where the installer has incorrectly wired elements in Location A 1002. Specifically, fiber 1004 originating from transmit transceiver TX-1 1006 is actually connected to input 1008 on add wavelength selective switch 1010, which is planned for fiber transmit receiver TX-2 1012. Furthermore, fiber 1014 originating from transmit transceiver TX-2 1012 is connected to input 1016 for add wavelength selective switch 1010, which is planned for transmit receiver TX-1 1006. In other words, the connections from the transceivers 1006, 1012 to the add wavelength selective switch 1010 are swapped on the inputs 1008, 1016 with respect to the planned deployment due to an installation error. In this incorrect configuration, at start-up, the transmitting transceiver TX-1 An add wavelength selective switch 1010, configured to route signals appearing on input 1016 from 1006, instead routes the signals appearing on input 1016 to transceiver TX-2 on its port 1016. 1012. The encoded configuration information provided on the low frequency control signal detected by the add wavelength selective switch 1010 allows this error to be immediately detected within the add wavelength selective switch 1010. In some methods of operation, the error can be corrected by having the hardware configuration network notify a client or third party manager that the wiring needs to be fixed. In other automatic methods of operation, the hardware configuration network automatically reconfigures the transceivers 1006, 1012 or automatically reconfigures the add wavelength selective switch 1010. The automatic reconfiguration is initiated based on control information sent to the optical elements that can be reconfigured to correct the error from the optical element that detected the error.

[0074] One aspect of the present teachings is the ability to provide a low-cost multi-transceiver combiner-splitter. FIG. 11 illustrates an embodiment of a low-cost combiner-splitter 1100 comprising hardware components according to the present teachings. Multiple transceivers 1102, 1102′ are connected to a passive combiner 1106 using multiple optical fibers 1104, 1104′. The passive combiner 1106 can include any number of ports. For example, the passive combiner 1106 can be a 16-port (16:1) passive combiner.

[0075] The output of the passive combiner 1106 is optically coupled to an optical amplifier 1110 using an optical fiber 1108. The optical amplifier 1110 is used to overcome the loss of the combiner 1106, which is approximately 13 dB for a 16:1 combiner. The optical amplifier 1110 can be a low-cost Erbium-doped fiber amplifier, which is widely available. For example, in one embodiment, the optical amplifier 1110 has a launch power of 0 dBm for each transceiver 1102, 1102' and sufficient amplifier gain to overcome the combiner loss, such that the output power from the amplifier 1110 is 12 dBm. The output of the optical amplifier 1110 is optically coupled to an optical splitter-combiner 1114 using an optical fiber 1112. The optical splitter-combiner 1114 includes a plurality of optical outputs 1116, 1116' that are optically coupled to a plurality of transceivers 1118, 1118'.

[0076] In various embodiments, the transceivers 1102, 1102' and the transceivers 1118, 1118' operate in either a transmit or receive mode. For example, in one method of operation, the transceivers 1102, 1102' operate in a transmit mode and the transceivers 1118, 1118' operate in a receive mode. In another method of operation, the transceivers 1102, 1102' operate in a receive mode and the transceivers 1118, 1118' operate in a transmit mode.

[0077] Some or all of the transceivers 1102, 1102', transceivers 1118, 1118', and amplifiers 1110 are configured using low frequency modulation as described herein. One feature of the hardware configuration network of the present teachings is that there is no need to record fiber ordering or mark specific transceiver connections because all configuration information can be provided by low frequency control signals. The configuration information enables automatic provisioning of tunable channels and establishes all data connections between the transceivers.

[0078] Some known optical transceivers provide digital diagnostics via a digital diagnostic monitoring interface (DDMI), which defines control information passed to a client or external management system, including information such as element identification information, element operating parameters, network and element configuration information, alarm and warning parameters, and vendor information. Digital diagnostic monitoring interfaces for small form factor (SFP) optical transceivers are detailed in Finisar Corporation Application Note AN-2030, "Digital Diagnostic Monitoring Interface for Optical Transceivers."

[0079] Known digital diagnostic monitoring interfaces include an interface device or optical transceiver that allows real-time access to device operating parameters, as well as alarm and warning flags that alert a user when operating parameters are outside of normal ranges. Known digital diagnostic monitoring interface devices generate diagnostic data by digitization of internally monitored analog signals. Calibration and alarm threshold data are typically written during interface device manufacture. In addition to generating digital readings of internal analog values, known digital diagnostic monitoring interface devices generate various status bits based on current values ​​and comparisons to factory preset values. Known digital diagnostic monitoring interface devices also generate identifier information.

[0080] Another aspect of the hardware configuration network of the present teachings is to provide enhanced digital diagnostic monitoring. Some embodiments of the hardware configuration network of the present teachings provide digital diagnostic monitoring interface control information as part of the low frequency control signals described herein. In particular, the low frequency control information is part of the low frequency control signals described herein and can include data fields that provide specific information for the transmitter component of the transceiver element. For example, the low frequency information signal can include one or more transmitter serial numbers for the transceiver element comprising the transmitter and / or a transmitter channel identification number for the particular 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 for the receiver component of the transceiver element. For example, the low frequency information signal can include one or more receiver serial numbers for the transceiver element comprising the receiver and / or a receiver channel identification number for the particular transceiver element.

[0081] Another aspect of the hardware configuration network of the present teachings is that it can provide extended digital diagnostics by exchanging configuration information with elements such as transceivers, amplifiers, wavelength filters, optical channel monitors, wavelength selective switches, wavelength multiplexers, wavelength demultiplexers, cross-connect devices, and optical switches. The extended digital diagnostic information is used as control information encoded on the optical control signals of the present teachings. The use of the optical control signals of the present teachings provides additional flexibility in the ability to reach various optical elements in the hardware configuration network compared to prior art configuration systems by selecting the appropriate optical carrier. In some embodiments of the hardware configuration network of the present teachings, the hardware configurable elements include photodiodes that decode the low frequency control signals described herein.

[0082] Those skilled in the art will appreciate that hardware configurable elements 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 used for network tuning before a transceiver transmitter becomes active. Furthermore, in some embodiments, the hardware configurable amplifier is configurable to have an optical gain that depends on an optical path noise calculation. Furthermore, in some embodiments, the hardware configurable amplifier gain profile is adjusted based on a channel configuration from a remote transceiver. Furthermore, in some embodiments, the hardware configurable amplifier can transmit information regarding the optical gain to the transceiver.

[0083] Further, in some embodiments, the hardware configurable wavelength selective switch ports are configured and reconfigured with flexible channel planning as required depending on the data traffic. Further, in some embodiments, the hardware configurable wavelength selective switch is used to provide network protection from failures by reconfiguring optical paths in the network after a failure. Further, in some embodiments, the hardware configurable optical programmable filters automatically adjust path distribution based on performance information provided by the hardware configurable transceiver elements without user or external network management intervention.

[0084] Additionally, in some embodiments, the hardware configurable optical channel monitor is calibrated using the low frequency control signals described herein. Referring to Figure 8, by adding high precision channel monitors 830, 832 and using the expanded digital diagnostic control information in a hardware configured network of the present teachings, the transceivers used in the network can be more tightly coordinated and spaced for higher aggregate optical transfer rates and spectral efficiency.

[0085] (Equivalent) While the applicant's teachings are described in conjunction with various embodiments, it is not intended that the applicant's teachings be limited to such embodiments. On the contrary, the applicant's teachings encompass various alternatives, modifications, and equivalents, which may be made thereto without departing from the spirit and scope of the present teachings, as will be appreciated by those skilled in the art.

Claims

1. A hardware-configured optical network element, comprising: an optical input adapted to receive an optical carrier containing client data traffic in a plurality of wavelength bands; a plurality of optical outputs, each of the plurality of optical outputs being optically connected to one of a plurality of downstream optical network elements via one of a plurality of transmission optical fibers; a wavelength selective switch adapted to output the client data traffic in each of the plurality of wavebands via a respective one of the plurality of optical outputs, and to impart modulation representing transmission control information to the client data traffic output via at least one of the plurality of optical outputs by modulating an attenuation of the client data traffic via the at least one of the plurality of optical outputs, a modulation frequency of the modulation imparted to the client data traffic being less than a modulation frequency of the client data traffic; A hardware configuration optical network element comprising:

2. A hardware configured optical network element as described in claim 1, wherein the wavelength selective switch is adapted to selectively provide the transmission control information to one or more of the plurality of wavelength bands output via the plurality of optical outputs.

3. A hardware configured optical network element as described in claim 2, wherein the wavelength selective switch is adapted to selectively provide the transmission control information to the one or more of the wavelength bands in accordance with an electronic control signal for selectively controlling the attenuation of the plurality of wavelength bands.

4. the plurality of optical outputs includes a first optical output for transmission to a first downstream optical network element and a second optical output for transmission to a second downstream optical network element; the input optical signal includes client data traffic in a first waveband from a first upstream optical network element and in a second waveband from a second upstream optical network element; the received control information includes instructions to pass the client data traffic from the first upstream optical network element to the first downstream optical network element; 2. The hardware-configured optical network element of claim 1, wherein the wavelength selective switch is adapted to output the client data traffic in the first waveband via the first optical output in accordance with the instructions to pass the client data traffic from the first upstream optical network element to the first downstream optical network element.

5. The optical network element according to claim 1, wherein the second downstream optical network element is configured to receive the client data traffic in the second wavelength band from the second upstream optical network element; the second downstream optical network element is adapted to identify a connection error in response to receiving client data traffic encoded with configuration information, the configuration information indicating that the received client data traffic is from the first upstream optical network element, and provide encoded corrective configuration information to the wavelength selective switch; 5. The hardware-configured optical network element of claim 4, wherein the wavelength selective switch is adapted to output the client data traffic in the first wavelength band via the second optical output and to output the client data traffic in the second wavelength band via the first optical output in response to the encoded corrective configuration information received from the second downstream optical network element.

6. The input optical signal further comprising receive control information generated by an upstream optical network element; the hardware-configured optical network element further comprising a demodulator adapted to form decoded control information by decoding the received control information; The hardware-configured optical network element of claim 1 , wherein the wavelength selective switch is configured according to the decoded control information.

7. The method of claim 1, wherein the decoded control information includes instructions to output at least one of the plurality of wavelength bands via one of the plurality of optical outputs; 7. The hardware-configured optical network element of claim 6, wherein the wavelength selective switch is adapted to output the at least one of the plurality of wavelength bands via the plurality of optical outputs in accordance with the decoded control information.

8. The hardware configured optical network element of claim 6, wherein the plurality of optical outputs of the wavelength selective switch are configured according to the decoded control information.

9. The hardware configured optical network element of claim 8, wherein the plurality of optical outputs are reconfigured in response to data traffic.

10. A hardware-configured optical network element as described in claim 9, wherein the decoded control information specifies a center frequency of each of the plurality of wavelength bands, or a bandwidth of each of the plurality of wavelength bands, or an attenuation level of the wavelength selective switch.

11. A hardware-configured optical network element, comprising: a first optical input port for receiving a first input optical signal from a first upstream optical network element, the first input optical signal including client data traffic from the first upstream optical network element and first received control information identifying the first upstream optical network element; a second optical input port for receiving a second input optical signal from a second upstream optical network element, the second input optical signal including client data traffic from the second upstream optical network element and second receive control information identifying the second upstream optical network element; a demodulator adapted to decode the first received control information to form first decoded control information and to decode the second received control information to form second decoded control information; a wavelength selective switch configured to receive the first input optical signal from the first upstream optical network element via the first optical input port and the second input optical signal from the second upstream optical network element via the second optical input port; Equipped with In response to receiving the second input optical signal from the second upstream optical network element via the first optical input port, the wavelength selective switch is adapted to identify a configuration error based on the second decoded control information identifying the second upstream optical network element.

12. The hardware-configured optical network element of claim 11, wherein the wavelength selective switch is automatically reconfigured to correct the configuration error.

13. The hardware configured optical network element of claim 11, wherein the wavelength selective switch is adapted to initiate an automatic reconfiguration by outputting transmission control information for transmission to an optical network element that can be reconfigured to correct the configuration error.

14. The method of claim 13, wherein the transmission control information is output for transmission to the first upstream optical network element and the second upstream optical network element; The hardware-configured optical network element of claim 13 , wherein the first upstream optical network element and the second upstream optical network element are automatically reconfigured according to the transmission control information to correct the configuration error.

15. A hardware-configured optical network element, comprising: a plurality of transmitting transceivers, each of the plurality of transmitting transceivers adapted to output a transmission optical signal including client data traffic in one of a plurality of wavelength bands; at least one modulator adapted to form the transmission optical signal output by the plurality of transmitting transceivers by applying a modulation representative of transmission control information to the client data traffic, the modulation frequency of the modulation applied to the client data traffic being less than a modulation frequency of the client data traffic; a passive combiner adapted to combine the transmission optical signals output by each of the plurality of transmitting transceivers to form a combined optical signal; and a passive optical splitter adapted to receive the combined optical signal and output the combined optical signal via each of a plurality of optical outputs; at least one demodulator, the at least one demodulator adapted to form decoded control information by decoding the control information; a plurality of receiving transceivers, each of the plurality of receiving transceivers adapted to receive the combined optical signal via one of the plurality of optical outputs; Equipped with the transmission control information identifies a plurality of data connections, each of the plurality of data connections defining one of the plurality of transmitting transceivers and one of the plurality of receiving transceivers; A hardware configured optical network element, wherein each receiving transceiver is adapted to identify the client data traffic in the waveband output by a transmitting transceiver defined in the data connection that defines the receiving transceiver.

16. The method of claim 15, wherein each of the plurality of transmitting transceivers receives the client data traffic output by the transmitting transceiver from an upstream optical network element; The hardware-configured optical network element of claim 15, wherein the received client data traffic is modulated in accordance with received control information.

17. The hardware-configured optical network element of claim 15, wherein each of the plurality of transmitting transceivers selects one of the plurality of wavelength bands in accordance with receiving control information.

18. The hardware-configured optical network element of claim 15, further comprising an optical amplifier adapted to receive the combined optical signal from the passive combiner, amplify the combined optical signal, and output the combined optical signal to the passive optical splitter.

19. The hardware configured optical network element of claim 18, wherein the optical gain of the optical amplifier is configured according to received control information that is imparted as modulation to the client data traffic.

20. The optical gain of the optical amplifier is set to overcome an optical loss imparted by an optical combiner; the reception control information is generated in response to a noise path calculation; The optical gain of the optical amplifier is set according to receive control information indicative of channel adjustment information received from one of the plurality of receiving transceivers; or 20. The hardware-configured optical network element of claim 19, wherein the optical amplifier transmits information indicative of the optical gain to the plurality of receiving transceivers, said transmitting being performed by imparting a modulation indicative of the information to the combined optical signal.

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