Subliminal coherent phase shift keyed in-band signaling of network management information in wavelength division multiplexed fiber optic networks

摘要

Optical communication systems and methods that provide subliminal in-band signaling of network management information in coherent phase shift keyed (PSK) optical networks. The advantages of this method over various prior art are twofold: (1) It does not require an extra wavelength division multiplexed optical channel to transmit network management data, and (2) it does not require expensive complete time division demultiplexing of the payload data to extract the network management information. The management channel data is transmitted in a spread spectrum signal format that is below the limit of detection in the transmission channel, hence the term subliminal. The subliminal signal is detected using correlative techniques (despreading). The spread-spectrum signal is a direct sequence binary PSK representation of the management channel data plus a spreading code. This spread spectrum signal is superimposed as a slow phase modulation on top of the transmitted high speed PSK payload signal. The high speed PSK data signal acts as a carrier of the spread spectrum signal to the receiver. The spread spectrum phase modulation has a deviation that is smaller than the root mean square phase noise in the fiber optic channel, thereby introducing no measurable increase in the required transmission bandwidth. The subliminally transmitted information is recovered using phase detection of the spread spectrum signal plus noise followed by a conventional despreading operation to raise the signaling information above the level of the received phase noise. The subliminally transmitted management channel info may be recovered at intermediate points in the fiber optic network without expensive complete electronic time division demultiplexing.