Described herein are photonic integrated circuits (PICs) comprising a semiconductor optical amplifier (SOA) to output a signal comprising a plurality of wavelengths, a sensor to detect data associated with a power value of each wavelength of the output signal of the SOA, a filter to filter power values of one or more of the wavelengths of the output signal of the SOA, and control circuitry to control the filter to reduce a difference between a pre-determined power value of each filtered wavelength of the output signal of the SOA and the detected power value of each filtered wavelength of the output signal of the SOA.

A method of optimizing optical signal quality in an optical communications link comprising a plurality of sections each comprising an optical amplification apparatus and an optical fiber span, the method comprising: for each section, determining a respective optimal optical channel power which minimizes a sum of an indication of a respective linear optical noise and an indication of a respective nonlinear optical noise; and generating and transmitting at least one control signal arranged to cause a target optical channel power of each section to be set to the respective optimal optical channel power.

An optical amplifier arrangement method includes an acquisition step of acquiring transmission path information indicating a configuration of a network that transmits an optical signal via a plurality of relay nodes and a transmission path of the optical signal transmitted by the network; and a determination step of determining arrangement of optical amplifiers in the network by grouping a plurality of optical fibers passing through the same relay node based on the transmission path information, and determining whether optical amplification is required in each of the relay nodes for each group of the optical fibers.

Embodiments of an optical amplification apparatus are disclosed which include a first optical amplifier, a second optical amplifier, and a mode exchanger. The first optical amplifier is connected to an input port of the mode exchanger, and the second optical amplifier is connected to an output port of the mode exchanger. The first optical amplifier is configured to amplify optical signals carried in a plurality of transmission modes of a few-mode fiber, the plurality of transmission modes of the few-mode fiber may be grouped into N groups, each group includes two transmission modes, and N is a positive integer greater than or equal to 1. The mode exchanger is configured to exchange the two transmission modes carrying optical signals in each group. The second optical amplifier is configured to amplify the optical signals that are carried in the two transmission modes in each group and whose modes are exchanged.