Wavelength multiplexing module with polarization maintaining fibers as depolarizers

A wavelength multiplexing module comprising:

• a plurality of pumping sources for outputting lights of different wavelengths;
• a wavelength multiplexer for multiplexing the lights output from the pumping sources, the wavelength multiplexer having optical input sections for respectively receiving the lights output from the pumping sources;
• and
• depolarizers, respectively provided between the optical input sections and the pumping sources,
• wherein each of the depolarizer causes a degree of polarization of the light output from an associated one of the pumping sources to approach zero;
• each depolarizer has two polarization-maintaining optical fibers connected in series on an optical path in such a way that primary optic axes of the polarization maintaining optical fibers obliquely intersect each other;
• a length L1 of a pumping-source side one of the two polarization-maintaining optical fibers is set equal to or greater than 50% of a shortest length that satisfies B·L1>Lc where Lc is a coherence length of the pumping sources and B is a value of a birefringence of the polarization-maintaining optical fibers;
• a length L2 of a wavelength-multiplexer side one of the polarization-maintaining optical fibers is set equal to or greater than twice the length L1 of the pumping-source side polarization-maintaining optical fiber;
• the lengths L1 of the pumping-source side polarization-maintaining optical fibers respectively connected to the plurality of pumping sources are set equal to one another;
• and
• the lengths L2 of the wavelength-multiplexer side polarization-maintaining optical fibers connected to the wavelength multiplexer are set equal to one another.

A wavelength multiplexing module comprising:

• a plurality of pumping sources for outputting lights of different wavelengths;
• a wave length multiplexer for multiplexing the lights output from the pumping sources, the wavelength multiplexer having optical input sections for respectively receiving the lights output from the pumping sources;
• and
• depolazizers, respectively provided between the optical input sections and the pumping sources,
• wherein each of the depolarizer causes a degree of polarization of the light output from an associated one of the pumping sources to approach zero;
• each depolarizer has one or more polarization-maintaining optical fibers provided on an optical path;
• and
• output-end side polarization-maintaining optical fibers of the depolarizers are connected to the wavelength multiplexer without aligning primary optic axes of the output-end side polarization-maintaining optical fibers with a primary optic axis of the wavelength multiplexer.