Mandrel bit Pc#

On singlemode fiber, PC finishes work even better at a slight angle (8º) to almost totally prevent reflectance (~ -60 dB). The technique involves polishing the end surface of the fiber to a convex surface to ensure proper fiber contact.

Several schemes have been used to reduce reflectance, mainly using a convex physical contact (PC) polish on the end of the connector ferrule, which reduces the fresnel reflection and reduces reflectance to ~-40 to -50 dB. Since this is more a problem with singlemode systems, manufacturers have concentrated on solving the problem for their singlemode components but multimode connectors benefit also since any reduction in reflectance also reduces loss. In multimode systems, reflections are less of a problem but can add to background noise in the fiber. Minimizing the reflectance is necessary to get maximum performance out of high bit rate laser systems and especially AM modulated CATV systems. Reflectance is one component of the connector's loss, representing about 0.3 dB loss for a non-contact or air-gap connector where the two fibers do not make contact. Properly made fusion splices will have no refelctance a reflectance peak indicates incomplete fusion or inclusion of an air bubble or other impurity in the splice. Mechanical splices have index matching gel to prevent reflections. See below for how OTDRs measure reflectance and return loss.Ĭonnectors have different ferrule end finishes to reduce reflectance as well as loss.

However, the term has been adopted by OTDR manufacturers to mean something different - the total of all reflectance events and total fiber backscatter over the entire length of fiber being tested. Optical return loss (ORL) is sometimes used as meaning the same as reflectance but, as the inverse of reflectance, has the opposite sign, e.g. Reflectance is primarily a problem with connectors but may also affect mechanical splices which contain an index matching gel to prevent reflectance. It is also called fresnel reflection and is caused by the light going through the change in index of refraction at the interface between the fiber (n=~1.5) and air (n=~1). Reflectance (which has also been called 'back reflection' or optical return loss ) of a connection is the amount of light that is reflected back up the fiber toward the source by light reflections off the interface of the polished end surface of the mated connectors and air. The FOA Reference For Fiber Optics - Measuring Reflectance or Return Loss Measuring Reflectance or Return Loss

Mandrel bit