A coherent optical transmitter includes circuitry connected to a coherent modulator; and a plurality of tunable optical filters (TOFs) connected to one another and connected to an output of the coherent modulator, wherein the plurality of tunable optical filters are configurable to create an effective transfer function having a variable width. The TOFs are cascaded and can be included in discrete form on electro-optic printed circuit boards (PCBs), or integrated in various electro-optic material systems such as in silicon photonics, photonic integrated circuits (PICs), as well as hybrid and other approaches. The advantage of this approach includes improved OSNR in colorless transmitters.

An optical receiver includes an error generator, a multipath interference estimator, and a combiner. The error generator is configured to receive an input comprising a received optical signal, to estimate a modulation level of samples of the received optical signal, and to generate an error signal based on the estimated modulation level of the samples, the error signal representing a difference between an actual level of the received optical signal and the estimated modulation level. The multipath interference estimator is configured to generate estimates of multipath interference (MPI) associated with the samples of the received optical signal based on the error signal. The combiner is configured to generate an MPI-mitigated signal based on a combination of the samples and the estimates of MPI.

An optical filter control apparatus according to the present disclosure includes: a compensation characteristic estimation unit configured to receive a received signal extracted from an optical signal that has passed through an optical filter provided in an optical transmission line and configured to transmit the optical signal having a predetermined frequency setting value, and estimate a compensation characteristic for compensating for waveform distortion due to a transmission path of the received signal; a frequency deviation estimation unit configured to estimate a frequency deviation between the frequency setting value and a reception frequency value acquired from the received signal; and a setting value calculation unit configured to calculate an optical filter setting value to be set in the optical filter by using the compensation characteristic adjusted based on the frequency deviation.

An optical receiver that includes an input port configured to receive intensity modulated optical signal with multipath interference (MPI); a detector configured to convert the intensity modulated optical signal with multipath interference to an electrical signal; a high pass filter (HPF) configured to filter the electrical signal and suppress carrier-carrier beat noise induced by the MPI to produce a filtered electrical signal; and an output port configured to transmit the filtered electrical signal.

A Reconfigurable Optical Add/Drop Multiplexer (ROADM) node architecture is disclosed that supports wide-spectrum channel operation. The ROADM includes a plurality of degrees, each degree comprising a Wavelength Selective Switch (WSS) configured to define variable-width spectral slices and perform spectral shaping or equalization. A central fiber/space switch interconnects slice ports of the WSSs and provides programmable partial-mesh connectivity. Local add/drop is achieved through direct connection of optical modems, including Full-Spectrum-Transponders (FSTs) that integrate multiple modems and internal multiplexing to provide wide-spectrum outputs spanning all or part of an amplified band. The fiber/space switch treats the FST as an add/drop degree, simplifying operations by eliminating intervening multiplexers and reducing external fiber connections. This architecture enables efficient end-to-end transport of wide spectral slices, reduces insertion loss, and allows scalable, cost-effective deployment of high-capacity ROADM nodes using existing optical components.

A method for equalization in an access network of passive optical network type. The method includes, for a given optical distribution network connecting a given input port of an optical line termination to a given plurality of optical network units: for at least one of the optical network units of the given plurality, obtaining a distance between the optical line termination and the optical network unit; determining a representative distance associated with the given optical distribution network, according to the one or more distances obtained; determining at least one equalization parameter, according to the representative distance; and equalizing transmission channels within the given optical distribution network, according to the at least one equalization parameter, each of the transmission channels connecting the given port of the optical line termination to one of the optical network units of the given plurality.

A variable optical attenuator (VOA) array is described, which may achieve a power adjustment speed of 1 ms or less for each channel. The VOA array includes: a substrate; and a plurality of VOAs disposed on the substrate, where the plurality of VOAs have trenches therebetween, and a VOA in the plurality of VOAs includes: a phase change material (PCM) layer, where a state of the PCM layer is selectively in a crystalline state, an amorphous state, or a mixed state based on temperature of the PCM layer, and variation of the state of the PCM layer is used for adjusting an output power of an optical signal input into the VOA array; a controller configured to change the temperature of the PCM layer; and a mirror layer configured to reflect the adjusted optical signal of the

Aspects of the disclosure are directed to a system for incorporating a CVBG (Chirped Volume Bragg Grating) into a prism to form a P-CVBG (Prism-Chirped Volume Bragg Grating) optical element for channel dispersion compensation. A prism region is configured to receive optical signals with multiple wavelengths and provide the wavelengths to the CVBG region by spatially separating the optical signals into various wavelengths. The CVBG region is configured to compensate for dispersion of the multiple wavelengths by reflecting the various wavelengths at different depths within the gratings of the CVBG region.