Due to increased volume of Internet traffic in recent years, power consumption of network equipment is increasing rapidly and intensified efforts have been made to enhance power-saving in networks. Under these circumstances, it has been found that cost-per-bit or power consumption per bit for switching traffic can be reduced by carrying out as much traffic processing in lower layers as possible. To realize this, many studies and activities have been conducted to establish an all-photonic network.
In an optical network constituting a metro core network, wavelength division multiplexing (WDM) is employed to deal with and carry a huge volume of traffic.
At these nodes handling WDM signals, wavelength selective switches (WSSs) are employed more and more as optical modules for carrying out Add/Drop or switching on a wavelength-by-wavelength basis.
A technique for reducing an amount of path computation for an optical path is proposed (see Patent Document 1). A path search technique capable of reducing processing time is also proposed (Patent Document 2). A WSS that can control degradation of pass-band characteristics is also known (Patent Document 3).