The system of a variable lightwave functional apparatus comprising: an optical amplifier for outputting wavelength multiplexed light containing a plurality of pulses having a first wavelength interval; a polarization branching/coupling device having a first port to a third port, for branching output from said optical amplifier, which is entered from said first port into the polarization branching/coupling device, to both said second port and said third port; a coupler arranged at the second port of said polarization branching/coupling device; and said variable lightwave functional circuit, and arranged between said third port of said polarization branching/coupling device and said coupler; wherein: said wavelength multiplexed light containing said plural pulses having said first wavelength interval is converted into wavelength multiplexed light containing a plurality of pulses having a second wavelength interval in response to lateral pressure applied to said polarization-maintaining optical fiber, and said coupler outputs said converted wavelength multiplexed light.