Optical fiber connector structure and characteristics

Optical fiber connectors are divided into optical fiber fixed connectors, that is, fixed connection between junctions. The methods of fixing joints include fusion splicing method, V-groove method, capillary method, casing method, etc. Optical fiber active connectors, commonly known as live joints, generally known as optical fiber connectors, are detachable connections between optical fiber lines and equipment.

Functions of Fiber Optic Connectors and Adapters

(1) Can form a continuous optical path

(2) Repeatable loading and unloading

(3) Actively connected with active or passive devices

(4) Active connection with systems and instruments

Widely used in long-distance trunk network, metropolitan area network, access network, optical fiber CATV network, optical fiber data network, DWDM system and other optical communication, optical sensor and other optical fiber application fields, it is currently the most used optical passive device.

The basic principle of an optical fiber connector is to use a certain mechanical and optical structure, and use an adapter to precisely butt the two end faces of the optical fiber to achieve physical contact between the optical fiber end faces. In order to maximize the coupling of the light energy output by the transmitting fiber into the receiving fiber.

Take FC/PC fiber optic connector and FC/PC as an example:

The connector can be divided into three parts according to the structure

1) Ceramic Ferrule

2) Connection structure (components)

3) Optical fiber cable

Features of fiber optic connectors:

1) Insertion loss

Refers to the number of decibels of the ratio of the output optical power to the input optical power after the optical signal in the optical fiber passes through the connector, and its expression is:

IL = -10Log

Where — optical power at the output end

- Input optical power

The smaller the insertion loss, the better, and the general requirement should be no more than 0.3dB. For multi-mode fiber connectors, the injected optical power should pass through a mode stabilizer to filter out higher-order modes, so that the modes in the fiber are distributed in a steady state, and the test loss is more accurate.

2) Return loss, that is, backward reflection loss. It refers to the decibel of the ratio of the retroreflected light to the input light at the fiber connection, and its expression is

= -10Log

- Retroreflected optical power

- Input optical power

The higher the return loss, the better to reduce the impact of reflected light on the light source and system. In the practical application of the connector, the surface of the pin has been specially polished, which can make the return loss larger, generally not less than 45dB.

3) Repeatability

Refers to the change of the insertion loss of the optical fiber (cable) movable connector after multiple insertions and removals, expressed in dB.

4) Interchangeability

Refers to the change in insertion loss when the components of the connector are interchanged, also expressed in dB. These two indicators can assess the rationality of the connector structure design and processing technology, and are also important indicators that indicate the practicality of the connector.

5) Mechanical properties

The mechanical properties of optical fiber connectors include axial retention strength, termination retention force, connection and separation force (moment), impact, torsion, cable retention force, extrusion resistance, external bending moment, vibration, shock, static load, etc. The use of various fiber optic connectors is different, and the requirements are different.

Mechanical durability refers to the number of times of plugging and unplugging of the fiber optic connector under normal use. The fiber optic connector currently used can generally be plugged and unplugged more than 1000 times.

6) Environmental performance

Environmental performance mainly includes: high temperature, temperature shock, humidity, sand and dust, ozone exposure, corrosion (salt spray), flammability, etc.