Patent ID: 8805191

Claim:
An optical fiber coupling assembly comprising: a dual core optical fiber pigtail for coupling at least first and second optical fibers to an optical sub-assembly, wherein the dual core optical fiber pigtail includes first and second optical fiber cores spaced with a predefined pitch, wherein the first optical fiber and the first optical fiber core are configured to carry light within a C-band wavelength range and an L-band wavelength range, and wherein the second optical fiber and the second optical fiber core are configured to carry light within the L-band wavelength range; a gradient index (GRIN) lens optically coupled to the optical fiber cores, wherein the GRIN lens is configured to bend light passing through the GRIN lens; and a wavelength division multiplexing (WDM) filter optically coupled to the GRIN lens, wherein the WDM filter is configured to pass light in the C-band wavelength range and to reflect light in the L-band wavelength range, wherein the WDM filter is optically coupled to the GRIN lens such that the light in the L-band wavelength range passing from the first optical fiber core through the GRIN lens is incident on the WDM filter at an incident angle allowing the light in the L-band wavelength range to reflect to the second optical fiber core, and wherein the WDM filter is optically coupled to a transmitting laser such that light is directed from the laser at the incident angle allowing the light in the C-band wavelength range to pass through the GRIN lens to the first optical fiber core and preventing back reflection of the laser light outside of the C-band wavelength range.