Optical module attenuator fiber looping

As light in fibers often does not have a well defined polarization state, it is important that a fiber-optic attenuator exhibits only a minimum amount of polarization dependence.Generally, the obtained insertion loss has some dependence on the optical wavelength. Some attenuators have a relatively strong wavelength dependence and are made for working in narrow wavelength regions, e.g. with a bandwidth of only 20 nm around a center wavelength of 1550 nm. Others are optimized for a weaker wavelength dependence, making them u. For single-mode devices, the insertion loss can not depend on the direction of propagation, as long as no non-reciprocal parts are used, as e.g. in a Faraday isolator. Fo...