Insert Loss and Return Loss for Fiber Connectors

Optical fiber connector is connected to various devices communication systems are essential components, is currently the largest use of optical devices. Since the local optical fiber communication network gradually, metro and access network users increased demand, global fiber optic connector market in recent years, the total demand continues to expand and the annual growth rate over the next decade is expected to be around 20%.

Although there are more than 70 kinds of Fiber Connectors, and new varieties are still emerging. Typically, the measure of product quality fiber optic connector optical characteristics of the main indicators Insert loss and Return loss. 

In addition, the impact of product quality and reliability ferrule endface geometry and other physical characteristics of the system indicators are increasingly being valued by manufacturers or end customers. The following from the fiber optic connector works starting on the connector insertion and return loss as a brief introduction:

Fiber optic connectors can’t be used, it must be the same with other types of connectors with each other, in order to form a light path connections. Insertion loss is the connector connecting the system with an optical power attenuation (i.e., the output power to the optical connector relative to the input power reduction amount). 

Variable Attenuator

Insertion loss mainly by optical phase between successive two lateral deviation caused. For example, two optical fibers in alignment, laterally offset is zero, then the result of the minimum insertion loss.

However, in the actual docking connector, this is unlikely to be achieved, since the core and the fiber cladding misalignment of the fiber cladding and the pin bore and the pin bore misalignment of the outer diameter of the concentric error, etc., will cause lateral deviation between the fibers.

Meanwhile, the fiber optic connector end face quality vertical clearances and insertion loss is caused by one of the factors commonly used in recent years, UPC plug contact way, you can solve the problem of vertical clearance. In this way, pins and fiber end is spherically polished, so that the two pins relative access under the action of external forces engaged with the engaging morph fiber and flattened, forming an optical fiber butt sufficient to reduce fiber connector vertical clearance.

Loopback Patch Cords

Return loss is a measure of the back end connector to the size of the parameters of reflected light. The essence of the echo that is reflected light, according to Fresnel reflection principle, the light during the transmission encounter two different refractive index interface Fresnel reflection occurs, causing the optical path of the signal is superimposed or interfere. In high data rate systems of single-mode fiber, in particular cable television system (CATV), reflections of the transmitted signal is generated a time lag, so that the signal time delay to reach the client, cause image ghosting and decreased sharpness.

UPC connector contacted manner, by reducing the gap between the connection end faces, in addition to reducing the insertion loss, but also reduces the connection end of the reflection and improve the return loss; while for other users of the CATV system, APC type contact method was a better choice: Because APC ceramic ferrule type connector end of its spherical axis normal to the fiber at an angle (usually 8 °), so that the light reflected from the end face escape without returning core, thus greatly improving the return loss of the connector.

Other info: Before installing any fiber optic system, you must first consider the approach to low-loss optical fiber or cable to connect to each other in order to achieve the optical link connection. Fiber link connection can be divided into permanent and activities of two kinds. Permanent connection, they use a fiber splicing method (related: fiber splicer), bonding method or fixed connector to achieve; activity of continuation, the general activities of the connector to achieve.

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