Abstract: An apparatus for measuring polarization dependent loss is disclosed featuring several fiber optic couplers combined in tandem and oriented such that the PDL noise of the measurement system is reduced to a negligible level. By matching the PDLs of the couplers and vectorally subtracting opposite phases of polarization, the PDL of the measurement system is virtually eliminated. Thus, the PDL noise floor is lowered to near zero and the PDL of the optical device-under-test (DUT) can be accurately measured. The system is relatively inexpensive to implement and offers needed versatility because it measures the PDL of optical devices that operate in a reflection mode or in a forward transmission mode. Thus, it provides one PDL measurement solution for both types of devices.

Abstract: An optical waveguiding fiber has a photosensitive core and a cladding that includes a photosensitive inner cladding region adjacent the core and an outer cladding region. The inner cladding region and the outer cladding region have substantially equal indices of refraction. The photosensitivity of the inner cladding region is sufficient to cause a modulation of the index of refraction of the inner cladding when exposed to ultraviolet light. In another aspect of the invention, the optical fiber includes a grating in the core, which extends radially into the inner cladding region. The core and the inner cladding region of the optical fiber are doped with concentrations of Ge and B sufficient to impart photosensitivity to the inner cladding region, and to result in an index of refraction in the inner cladding region substantially equal to the index of refraction of the outer cladding region.

Abstract: An apparatus for measuring polarization dependent loss is disclosed featuring several fiber optic couplers combined in tandem and oriented such that the PDL noise of the measurement system is reduced to a negligible level. By matching the PDLs of the couplers and vectorally subtracting opposite phases of polarization, the PDL of the measurement system is virtually eliminated. Thus, the PDL noise floor is lowered to near zero and the PDL of the optical device-under-test (DUT) can be accurately measured. The system is relatively inexpensive to implement and offers needed versatility because it measures the PDL of optical devices that operate in a reflection mode or in a forward transmission mode. Thus, it provides one PDL measurement solution for both types of devices.