A transmitting device, includes inputting a multiplex light multiplexed a first wavelength-multiplexed signal light stream in a first wavelength band and a second wavelength-multiplexed signal light stream in a second wavelength band; inputting a multiplex light multiplexed a third wavelength-multiplexed signal light stream in a first wavelength band and a fourth wavelength-multiplexed signal light stream in a second wavelength band; converting the first wavelength-multiplexed signal light stream to the second wavelength band; converting the third wavelength-multiplexed signal light stream to the second wavelength band; generating a first output signal light multiplexed by signal light in a first wavelength band among the multi-wavelength light so that wavelengths do not overlap; generating a second output signal light multiplexed by signal light in a second wavelength band among the multi-wavelength light so that wavelengths do not overlap; converting the first output signal light to the first wavelength band; and outputting the multiplexed light.

A system for protecting optical paths may exchange first optical signal traffic between source and destination locations over a first fiber cable comprising optical signals having wavelengths within a first predefined optical wavelength band, exchange second optical signal traffic between the source and destination locations over a second fiber cable comprising optical signals having wavelengths within the first optical wavelength band, convert the first optical signal traffic to third optical signal traffic comprising optical signals having wavelengths within a second predefined optical wavelength band, detect an interruption in the exchange of the first optical signal traffic and, in response to detecting the interruption, cause the third optical signal traffic to be carried from the first location to the second location over the second fiber cable in the second optical wavelength band while the second optical signal traffic is exchanged over the second fiber cable in the first optical wavelength band.

A transmission device, includes a first wavelength converter configured to convert a second wavelength-multiplexed signal in a first wavelength band to a second wavelength band different from the first wavelength band, and a multiplexer configured to transmit, after the conversion, a wavelength-multiplexed signal obtained through multiplexing of a first wavelength-multiplexed signal in the first wavelength band, a first supervisory control signal light ray that is a control signal for the first wavelength-multiplexed signal, the second wavelength-multiplexed signal in the second wavelength band, and a second supervisory control signal light ray that is a control signal for the second wavelength-multiplexed signal, wherein the first supervisory control signal light ray and the second supervisory control signal light ray each have a wavelength in a wavelength band different from the first wavelength band and the second wavelength band.

An optical transmission apparatus includes a splitter configured to split a first wavelength division multiplexed optical signal arranged in a first wavelength band and a second wavelength division multiplexed optical signal arranged in a second wavelength band, respectively, from an optical signal including the first wavelength division multiplexed optical signal and the second wavelength division multiplexed optical signal, a wavelength converter configured to convert a wavelength of the split second wavelength division multiplexed optical signal to generate a third wavelength division multiplexed optical signal to be arranged in the first wavelength band, an optical monitor configured to monitor power of each wavelength channel of the third wavelength division multiplexed optical signal, and a transmitter configured to transmit a monitoring result by the optical monitor to a transmission source node of the optical signal or a relay node of the optical signal.

An optical transmission apparatus includes a splitter configured to split a first wavelength division multiplexed optical signal arranged in a first wavelength band and a second wavelength division multiplexed optical signal arranged in a second wavelength band, respectively, from an optical signal including the first wavelength division multiplexed optical signal and the second wavelength division multiplexed optical signal, a wavelength converter configured to convert a wavelength of the split second wavelength division multiplexed optical signal to generate a third wavelength division multiplexed optical signal to be arranged in the first wavelength band, an optical monitor configured to monitor power of each wavelength channel of the third wavelength division multiplexed optical signal, and a transmitter configured to transmit a monitoring result by the optical monitor to a transmission source node of the optical signal or a relay node of the optical signal.

The embodiments disclosed herein provide fast recovery of a network signal path by, in the event of a failure or unacceptable degradation in a signal in the original network path, diverting the optical signal passing through the network to a preselected bypass optical path which is maintained in a warm or operational state. The optical elements on the bypass optical path are available network resources which may, during part or all of the time the bypass path is designated for a node in the primary optical path, be in use to transmit other optical signals in the network. By maintaining the resources in the designated bypass path in a warm or operating state, fast rerouting and recovery of an interrupted signal is possible.

A wavelength cross-connect device performs relay processing, the relay processing being such that wavelength multiplexed signal lights, which are multiband transmitted from a plurality of routes, are demultiplexed into different wavelength bands, and for each route, respective optical signals of the different wavelength bands are amplified, then subject to route change by WSSs and outputted to output side routes M. The device includes C-band WXC units that are the same in total number as the wavelength bands of the optical signals of the respective wavelength bands and perform relay processing on optical signals of a specific wavelength band of the different wavelength bands.

A fast optical (with or without a photonic crystal) switch is fabricated/constructed, utilizing a phase transition material/Mott insulator, activated by either an electrical pulse (a voltage pulse or a current pulse) and/or a light pulse and/or pulses in terahertz (THz) frequency of a suitable field strength and/or hot electrons. The applications of such a fast optical switch for an on-demand optical add-drop subsystem, integrating with (a) a light slowing/light stopping component (based on metamaterials and/or nanoplasmonic structures) and (b) with or without a wavelength converter are also described.

An optical transmission system comprises at least one first connection point and one second connection point arranged to transmit and receive at least one channel signal transmitted via at least one optical means connecting the first connection point and the second connection, wherein each of the at least one channel signal is reversibly configurable to be transmitted in either a first direction or a second direction between the first connection point and the second connection point. A method of transmitting at least one channel signal between a first connection point and a second connection point via at least one optical media in an optical transmission system, wherein each of the at least one channel signal is reversibly configurable to be transmitted in either a first direction or a second direction between the first and the second connection points.

An optical node device includes: an optical switch coupled to a multicore fiber that has N (N is an integer of 2 or more) cores; a multiplexer-demultiplexer coupled to a single-core fiber that multiplexes and transmits optical signals in M (M is an integer of 2 or more; and M?N) bands; a maximum of (M?1) wavelength converters provided between the optical switch and the multiplexer-demultiplexer; and a control circuit that controls the optical switch, the wavelength converter or both of the optical switch and the wavelength converter and the control circuit controls the optical switch or the wavelength converter or both of the optical switch and the wavelength converter such that, of the optical signals in the M bands, an optical signal in at least one band is not subject to wavelength conversion and an optical signal in another band is subject to the wavelength conversion.