Polarization-combining fused-fiber optical coupler and method of producing the same

A polarization-combining fused-fiber optical coupler comprising:

• a coupling zone made of two non-birefringent single-mode (SM) fibers fused and drawn so as to form an adiabatic tapered profile, said coupling zone having two input arms and two output fibers;
• and two polarization maintaining (PM) fibers having light input ends and light output ends, said output ends of the PM fibers being spliced to the input arms of the coupling zone, so that when linearly polarized light is injected into the input ends of each PM fiber and oriented to make polarization in one PM fiber orthogonal to that of the other PM fiber at the output ends of the PM fibers, and when said light from the two PM fibers then passes through the input arms into the coupling zone, said coupling zone combines maximum transmitted power of the two polarizations at a desired common wavelength in one output fiber, with only a minimal power transmission going to the second output fiber;
• characterized in that the coupling zone is so shaped as to achieve a power transmission of the order of 99% in said one output fiber.

A polarization-combining fused-fiber optical coupler comprising:

• a coupling zone made of two non-birefringent single-mode (SM) fibers fused and drawn so as to form an adiabatic tapered profile, said coupling zone having two input arms and two output fibers;
• and two polarization maintaining (PM) fibers having light input ends and light output ends, said output ends of the PM fibers being spliced to the input arms of the coupling zone, so that when linearly polarized light is injected into the input ends of each PM fiber and oriented to make polarization in one PM fiber orthogonal to that of the other PM fiber at the output ends of the PM fibers, and when said light from the two PM fibers then passes through the input arms into the coupling zone, said coupling zone combines maximum transmitted power of the two polarizations at a desired common wavelength in one output fiber, with only a minimal power transmission going to the second output fiber;
• characterized in that the coupling zone is 15 to 20 mm long and has a wavelength bandwidth greater than 8 nm for an isolation of at least 17 dB.

A polarization-combining fused-fiber optical coupler comprising:

• a coupling zone made of two non-birefringent single-mode (SM) fibers fused and drawn so as to form an adiabatic tapered profile, said coupling zone having two input arms and two output fibers;
• and two polarization maintaining (PM) fibers having light input ends and light output ends, said output ends of the PM fibers being spliced to the input arms of the coupling zone, so that when linearly polarized light is injected into the input ends of each PM fiber and oriented to make polarization in one PM fiber orthogonal to that of the other PM fiber at the output ends of the PM fibers, and when said light from the two PM fibers then passes through the input arms into the coupling zone, said coupling zone combines maximum transmitted power of the two polarizations at a desired common wavelength in one output fiber, with only a minimal power transmission going to the second output fiber;
• characterized in that the second output fiber has a termination adapted to prevent optical return losses.