A route switching device includes a first selection section for outputting a first main signal, a second selection section for outputting a first switching command signal, a first transmitter transmitting an inputted signal, a second transmitter, a first receiver, a second receiver, a first monitor for outputting an abnormality notification if an abnormality in a second main signal is detected, and outputting a first switching command notification if second information is included in a second switching command signal, a second monitor, and a third selection section for obtaining a second main signal from a selected receiver. The first selection section and the second selection section switches a selection destination when a first switching command notification is input. The second selection section outputs a switching command signal including second information when an abnormality notification is input. The third selection section switches a selection source when an abnormality notification is input.

Systems and methods for performing wavelength conflict detection are provided. These are to detect situations in optical networks where two instances of the same wavelength channel have been added. Wavelength conflict detection is performed for each of a plurality of possible wavelength channels that could be present in an optical signal, each wavelength channel that is present modulated by a pilot tone signal with a respective pilot tone frequency, the pilot tone signal carrying M-ary pilot tone data, M=2.sup.n, n?1, with a respective one of M different sequences being used to represent each of M possible data values over a data value period. Conflict detection for each wavelength channel involves performing correlation peak detection using each of the M different sequences to determine correlation peaks for each of the M different sequences, and, based on the determined correlation peaks, determining whether multiple instances of the wavelength channel are present in the optical signal.

An optical transmission device and an optical communication system being capable of coping with various installation forms of a transponder in a unit of optical fiber transmission path are provided. The optical transmission device is installed inside a station building. First and second interface units are connected to first and second fiber transmission paths accommodated in a submarine optical fiber cable. A first fiber transmission path mediates an optical signal to be transmitted between the first interface unit and a first transponder. A second fiber transmission path mediates an optical signal to be transmitted between the second interface unit and a second transponder.

An optical signal transmitted by another terminal device that was used for compensation could be received by a device that is not the intended destination of said optical signal, resulting in the problem that confidentiality cannot be guaranteed for the information in said optical signal. This optical reception device is characterized by the provision of the following: a receiving means via which wavelength-multiplexed signal light is inputted; and a transmitting means that, in accordance with an identifier in an optical signal of a prescribed wavelength in the inputted wavelength-multiplexed signal light, forwards said optical signal.

A dummy light module includes a dual semiconductor optical amplifier (SOA) light source configured to emit two substantially identical light emissions. The two light emissions include a first light emission and a second light emission, both having a first polarization. The dummy light module further includes a polarization rotator configured to rotate the second light emission to a second polarization, and a polarization beam combiner configured to generate dummy light by combining the first light emission with the first polarization and the second light emission with the second polarization.

A method of loading a fiber optic transport system includes adding one or more control channels to an optical fiber having one or more channels, wherein each of the control channels comprises a pair of signals that are cross-polarized and each of the pair of signals is at a different frequency from one another; measuring optical power on the optical fiber; and adjusting optical power of the one or more control channels based on the measured optical power.

A method and system for transient and switching stabilization of a fiber optic transport system. One or more data-bearing channels are coupled to an optical fiber. The data-bearing channels are distributed among a plurality of frequency sub-bands. A set of control channels is also coupled to the optical fiber. Each control channel includes a pair of signals at separate frequencies. There is at least one control channel in each of the plurality of frequency sub-bands. The pair of signals of a control channel are cross-polarized. Optical power in at least one of the plurality of sub-bands is measured. Responsive to the measured optical power, the optical power of a control channel is adjusted to maintain a substantially constant power of a sub-band that contains the adjusted control channel.

A reconfigurable optical add/drop multiplexer (ROADM) unit includes a first optical circulator coupled to a first terminal; a second optical circulator coupled to a second terminal; a third optical circulator coupled to a third terminal; a fourth optical circulator coupled to a fourth terminal; a first wavelength-selective switch (WSS), coupled to the first, second, and third optical circulators; a second WSS coupled to the first, second, and fourth optical circulators, wherein the first and second WSSes are bidirectional operated; a first 1:2 coupler positioned between the first circulator and the first and second WSSes; a second 1:2 coupler positioned between the second circulator and the first and second WSSes.