An optical transmitter generates symbols for transmission by applying a predetermined coding method to each of m-valued transmission symbols generated from transmission data, generates signal light by performing optical modulation on the basis of the symbols for transmission, and transmits the signal light. An optical receiver generates a series of digital signals from the received signal light, detects coded symbols by applying predetermined digital signal processing to the series of digital signals, decodes the m-valued transmission symbols from the detected coded symbols, and restores the transmission data from the decoded m-valued transmission symbols. An operation based on the predetermined coding method performs nonlinear coding that generates the coded symbols by generating m-valued intermediate symbols from the m-valued transmission symbols, the nonlinear coding restricting transitions between series of the coded symbols in time series by assigning bit information to a state transition between coded symbols adjacent in time series and making a number of states that each of the coded symbols can take on greater than a number of states of the m-valued transmission symbols.

A relay apparatus 400 performs control to measure a first signal quality of a radio signal from a smart meter 300 and present the first signal quality to a user. The relay apparatus 400 establishes a radio connection with the smart meter 300 having a radio communication function. The relay apparatus 400 relays communication between the smart meter 300 and the power management apparatus 200.

One or more servers may receive an instruction to change a modulation format, associated with one or more optical channels, from a first modulation format to a second modulation format; provide the instruction to change the modulation format to a network device, associated with the one or more optical channels, to cause the network device to change the modulation format, associated with the one or more optical channels, from the first modulation format to the second modulation format; and determine that a license repository is to be updated based on receiving the instruction to change the modulation format. The license repository may store one or more licenses. The one or more servers may generate a license update instruction to update the license repository based on determining that the license repository is to be updated and output the license update instruction to cause the license repository to be updated.

A digital signal processor (DSP) interface apparatus capable of variably setting an interconnection between a DSP and a plurality of hardware devices and a method of controlling the same are provided. The DSP interface apparatus includes a path setter configured to set a data transmission path between at least one of a plurality of hardware devices and a DSP; and a controller configured to control the path setter to set the data transmission path by connecting at least one of a plurality of operation parts and a memory of the DSP and at least one of the plurality of hardware devices based on predetermined configuration information.