Optical add-drop multiplexer

An optical signal deterioration monitor system comprising an optical add-drop multiplexer which is provided in each node of an optical network, for adding, dropping or passing a wavelength multiplexed optical signal, and monitors an optical signal fault within the optical network, said optical add-drop multiplexer comprising:

• an optical wavelength division coupler for wavelength-dividing a wavelength multiplexed light input from one optical transmission line to a plurality of wavelength lights having different wavelengths;
• a plurality of light receivers for receiving the respective wavelength different wavelengths output from said optical wavelength division coupler;
• a plurality of optical gate switches each for on-off controlling a therethrough;
• a plurality of light transmitters provided correspondingly to the plurality of said light receivers, each said fight transmitter transmitting a different one of the plurality of wavelength lights having different wavelengths constituting the wavelength multiplexed light;
• an optical wavelength multiplexer coupler for receiving fight outputs of said optical gate switches and light outputs of said light transmitters and sending a wavelength multiplexed tight to the other optical transmission line;
• and
• an optical signal deterioration monitor means comprising
• means for monitoring an optical signal fault by either detecting an optical loss of signal by determining presence or absence of a signal light on a basis of calculation of an optical S/N ratio from a ratio of intensity of light within a wavelength range of a predetermined width including at least the signal light to intensity of spontaneously emitted fight having wavelength within a different wavelength range of substantially the same width as the predetermined width or determining presence or absence of the signal light from intensity of light within a wavelength range of a certain width including the signal light, or detecting the optical loss of wavelength by monitoring wavelength deviation of the signal fight from intensity of light within the wavelength range;
• means for calculating an optical S/N ratio from a ratio of intensity of fight within a wavelength range of a predetermined width including at least the signal light to intensity of spontaneously emitted light having wavelength within a different wavelength range of substantially the same width as the predetermined width and detecting the optical signal degrade when the optical S/N ratio becomes smaller than a predetermined threshold value;
• and
• means for converting a fault signal into the optical alarm indication signal in an optical layer by cutting off a signal output correspondingly to an input when said optical signal deterioration monitor means detects in the input the fault signal of either the optical loss of signal, the optical loss of wavelength or the optical signal degrade and noticing the optical alarm indication signal to said nodes on the downstream side.

An optical signal deterioration monitor system including an optical network having;

• an optical add-drop multiplexer for adding, dropping or passing a wavelength multiplexed optical signal;
• an optical repeater/amplifier for amplifying and repeating a wavelength multiplexed light;
• and
• a line terminator for terminating an optical signal and converting the optical signal into a signal of SONET/SDH standard, wherein each of said optical add-drop multiplexer and said optical repeater/amplifier comprises:
• optical signal deterioration monitor means including means for monitoring an optical signal fault by either detecting the optical loss of signal by determining presence or absence of a signal light on a basis of calculation of an optical S/N ratio from a ratio of intensity of light having wavelength within a wavelength range of a predetermined width including at least the signal light to intensity of spontaneously emitted light having wavelength within a different wavelength range of substantially the same width as the predetermined width or determining presence or absence of the signal light from intensity of light having wavelength within a certain wavelength range including the signal light, or detecting the optical loss of wavelength by monitoring wavelength deviation of the signal light from intensity of light having wavelength within the wavelength range;
• means for calculating an optical S/N ratio from a ratio of intensity of light having wavelength within a wavelength range of a predetermined width including at least the signal light to intensity of spontaneously emitted light having wavelength within a different wavelength range of substantially the same width as the predetermined width and detecting the optical signal degrade when the optical S/N ratio becomes smaller than a predetermined threshold value;
• and
• means for converting a fault signal into an optical alarm indication signal in an optical layer by cutting off a signal output correspondingly to an input when said optical signal deterioration monitor means detects in the input the fault signal of either the optical loss of signal, the optical loss of wavelength or the optical signal degrade and noticing the optical alarm indication signal to said nodes on the downstream side, wherein, in order to notice a network fault occurrence to said line terminator on the downstream side on the detection location of the network fault when the network fault is detected in a section layer of the SONET/SDH in said optical network, an optical signal cut-off fault in said network is monitored by at least one of the optical loss of signal and the optical alarm indication signal in said optical layer instead of an line alarm indication signal in the SONET/SDH layer output again to said line terminator to notice the network fault to said line terminator by reading in the line alarm indication signal assigned to a line overhead to identify the network fault.