fiber optic coupler

Optical fiber coupler (Coupler), also known as splitter (Splitter), connector, adapter, fiber optic flange, is a component used to realize optical signal splitting/combining, or to extend optical fiber links, and belongs to optical passive components Fields, it will be applied in telecommunication network, cable TV network, user loop system, and regional network.

Single Mode Fiber Coupler

Single-mode fiber couplers are the most widely used. 2&TImes; 2 The single-mode fiber coupler is typical, and its composition is shown in the figure. It has two input ports and two output ports with a coupling section in between. Figure 2(a) is made by melt stretching process. The stretched portion forms a tapered coupling region. Stretching expands the light energy in the core region to the outside of the core; at the same time, it brings the two cores closer to each other, both of which enhance the coupling. The optical signal input by 1 or 2 is distributed through the tapered coupling area, and output by 3 and 4 terminals.

The ratio of distribution is called the coupling ratio and is controlled by the length of the stretching zone. In (b) in the figure, the optical fiber with a certain curvature embedded in the quartz block is used to remove part of the cladding, and then two such quartz blocks are pressed together to make the two cores close to each other to form a fiber coupler. The coupling ratio is determined by the proximity of the cores and the radius of curvature of the fiber in the silica block. The coupling ratio can be selected between 1% and 99%, and the insertion loss is less than 0.5dB. The optical signal coupled by the input light in the opposite direction is extremely weak, so the fiber coupler is often called a directional coupler.

Multimode Fiber Coupler

The principle and structure of the multimode fiber coupler are basically similar to those mentioned above, except that the grinding and polishing device requires strong coupling, so the grinding and polishing plane enters the fiber core. On the basis of grinding and polishing 2&TImes; 2 fiber optic couplers, adjustable couplers can also be made. In the case of a certain wavelength, the coupling ratio changes with the angle formed by the two polished fibers, so the coupling ratio can be changed by adjusting the relative direction of the two optical fibers.

In the optical fiber local network or other occasions, l&TImes; N, N&TImes; 1 coupler or N×M coupler (or star coupler), in which the first number represents the number of input terminals, and the second number represents the number of output terminals. These couplers are made by fusion drawing method.

The role of fiber coupler

The optocoupler consists of two parts: the light source and the light receiver. The light-emitting source and the light-receiving device are assembled in the same airtight casing, and they are separated by transparent insulators. The pin of the light source is the input end, and the pin of the light receiver is the output end. The common light source is a light-emitting diode, and the light receiver is a photodiode, phototransistor, etc.

The role of the fiber coupler is to realize the splitting/combining of optical signals, or the components used to extend the optical fiber link. applicable to.

Instructions

In use, connect two sections of fiber optic lines to the two interfaces of the fiber coupler, and then combine them together. Different types of fiber optic couplers have different forms and are mainly based on specific products.

Classification

According to the different coupling fibers, there are the following classifications:

SC fiber optic coupler: applied to the SC fiber optic interface, it looks similar to the RJ-45 interface, but the SC interface is flatter, the obvious difference is the contacts inside, if there are 8 thin copper contacts, then It is an RJ-45 interface, and if it is a copper column, it is an SC optical fiber interface.

LC fiber optic coupler: It is applied to LC fiber optic interface and connects to the connector of SFP module. It is made of a modular jack (RJ) latch mechanism that is easy to operate. (commonly used by routers)

FC fiber optic coupler: applied to FC fiber optic interface, the external strengthening method is a metal sleeve, and the fastening method is a turnbuckle. Generally used on the ODF side (the most used on the distribution frame)

ST fiber optic coupler: applied to ST fiber optic interface, often used in fiber optic distribution frame, the shell is round, and the fastening method is a turnbuckle. (For 10Base-F connection, the connector is usually ST type. Commonly used in fiber distribution frame)