Patent ID: 6215572
Filing Date: 2001-04-10
Classification: H04J

Abstract:
A wavelength division multiplexing optical transmission apparatus for modulating light signals emitted from a plurality of light sources having respective different oscillation wavelengths with individual electric signals with respect to light intensity, combining these light signals into a single combined light signal and then transmitting the combined light signal onto a transmission line; said apparatus comprising:an optical coupler for branching part of the combined light signal;an optical band pass filter having a function of determining a wavelength of a transmitted light signal according to a driving voltage value of a periodically-varying driving electric signal externally supplied thereto and for passing therethrough light signals each having a single wavelength from the combined light signal received from said optical coupler in a predetermined wavelength order of all the wavelengths according to the driving voltage value of said periodically-varying driving electric signal;an optical detector, when receiving said transmitted light signal from said optical band pass filter, for photoelectrically converting the received light signal to a detection pulse and outputting the detection pulse;a driving voltage identifying circuit for receiving the detection pulse from said optical detector and said external driving electric signal, detecting the detection voltage value of the driving electric signal each time the driving voltage identifying circuit receives the detection pulse, holding and sending the detection voltage value of one specific order for each period of the driving electric signal, resetting the detection voltage value, finding a difference between two sequentially-detected detection voltage values corresponding to the adjacent wavelengths of the light signals, and externally issuing an alarm when the difference is equal to or smaller than a set value; anda control circuit for receiving the detection voltage value received from said driving voltage identifying circuit for each period and for controlling an oscillation wavelength of one of the light sources corresponding to a reference voltage value to be constant, one of the detection voltage values for the first period being used as said reference voltage value.