The present disclosure includes methods and systems in which idle tones are added at an ingress and terminated at an egress of a given fiberoptic communication link between ROADM nodes. An equalization process can be performed across the spectrum of available wavelength channels and then a determination can be made of a number of channels that can be added or dropped at a given time that meet a maximum threshold for change in power of the channels in the available wavelength. As channels without information-carrying signals are filled with idle tones, the stability of the optical system can be improved as there is less variability in power change when all of the channels have a substantially similar nominal power and a signal on one or more of those channels are added or removed.

An optical communication system which is tunable and polarization insensitive is provided herein. The optical communication system may comprise an optical bench coupling an optical transmit pathway and an optical receiving pathway to an external pathway. The optical bench includes a polarization insensitive optical circulator. The system may further include a tunable component positioned along the optical receiving pathway, and a controller coupled to the tunable component.

Techniques for improving gain equalization in C- and L-band (C+L) erbium-doped fiber amplifier (EDFAs) are provided. For example, the C- and L-band amplification sections of a C+L EDFA may be separated and configured in a parallel arrangement or a serial arrangement. For both the parallel and serial arrangements, the C- and L-band amplification sections may share a common gain flattening filter (GFF) or each amplification section may include and employ a separate GFF. Moreover, in some examples, an interstage L-band GFF may be located before or upstream of the L-band amplification section such that the L-band optical signal is gain-equalized or flattened prior to the L-band amplification section amplifying the L-band.

A device for generating wide capture range frequency tunable optical millimeter-wave signal includes a millimeter-wave signal generating structure, a millimeter-wave signal modulation structure, an optical delay phase detection structure and a feedback control loop. The millimeter-wave signal generating structure obtains millimeter-wave signal by beat frequency of the optical signal generated by a master laser and a slave laser, the millimeter-wave signal is modulated onto an optical carrier of the master laser by the electro-optical modulation structure, and then passes through the optical delay phase detection structure to generate an error signal associated with a frequency of the millimeter-wave signal. The error signal is controlled by the feedback control loop to change temperature and driving current of the slave laser, and adjust a difference between output wavelengths of the master laser and the slave laser, and at last maintain the frequency and phase of the millimeter-wave be stable.

A receiver (e.g., for a 10G fiber communications link) includes an interleaved ADC coupled to a multi-channel equalizer that can provide different equalization for different ADC channels within the interleaved ADC. That is, the multi-channel equalizer can compensate for channel-dependent impairments. In one approach, the multi-channel equalizer is a feedforward equalizer (FFE) coupled to a Viterbi decorder, for example, a sliding block Viterbi decoder (SBVD); and the FFE and/or the channel estimator for the Viterbi decoder are adapted using the LMS algorithm.

Multiple receivers are comprised in a flexible coherent transceiver of a multi-span optical fiber network. Each of the multiple receivers is operative to handle communications on a respective channel. The multiple receivers measure optical characteristics. For each of the multiple receivers, the optical characteristics include optical nonlinear interactions on the respective channel, the optical nonlinear interactions being at least partially dependent from one span to another span. An optical power of a signal on each of the multiple channels is adjusted as a function of the optical characteristics.

The present disclosure includes methods and systems in which idle tones are added at an ingress and terminated at an egress of a given fiberoptic communication link between ROADM nodes. An equalization process can be performed across the spectrum of available wavelength channels and then a determination can be made of a number of channels that can be added or dropped at a given time that meet a maximum threshold for change in power of the channels in the available wavelength. As channels without information-carrying signals are filled with idle tones, the stability of the optical system can be improved as there is less variability in power change when all of the channels have a substantially similar nominal power and a signal on one or more of those channels are added or removed.

A dynamic gain equalizer (DGE) for an optical communication device and related method which are capable of reducing power variations among wavelength division multiplexing (WDM) signals. The DGE and method use an optical attenuation device configured such that the ratio of pixel gap distance to the channel beam diameter at the point of incident to the optical attenuation device is less than or equal to 0.06. The DGE can produce output signal sets that have ripple increases of less than 0.1 db over the input signal sets.

An optical communication device and related method are provided for reducing power variations among wavelength division multiplexing (WDM) signals. The device includes a dynamic gain equalizer (DGE) coupled to an optical communication path carrying WDM optical signals. The DGE is controlled in response to signals generated by an optical channel monitor (OCM). The OCM monitors signals coming into the DGE and monitors the signals leaving the DGE to thus monitor the WDM spectrum for optical signal power variations and adjust the DGE to reduce the signal power variations.

Techniques for improving gain equalization in C- and L-band (C+L) erbium-doped fiber amplifier (EDFAs) are provided. For example, the C- and L-band amplification sections of a C+L EDFA may be separated and configured in a parallel arrangement or a serial arrangement. For both the parallel and serial arrangements, the C- and L-band amplification sections may share a common gain flattening filter (GFF) or each amplification section may include and employ a separate GFF. Moreover, in some examples, an interstage L-band GFF may be located before or upstream of the L-band amplification section such that the L-band optical signal is gain-equalized or flattened prior to the L-band amplification section amplifying the L-band.