Fiber optic connector loss

What is the key point of fiber optic connector insertion loss?

1. Main factors of connector insertion loss

(1) Fiber structure parameters

(Different fiber core diameters, different numerical apertures, different refractive index distributions, etc.) The loss caused by mismatch.

(2) Core alignment error (core misalignment loss)

Losses due to lateral misalignment of the core are called misalignment losses. This is an important cause of insertion loss.

There are many reasons for this loss. It mainly includes the core/cladding concentricity of the optical fiber, the concentricity of the ferrule and the unsatisfactory test adapter parameters.

(3) Loss due to end face shape and clearance

The main reason for this loss is that the physical parameters of the end face of the carrier-grade optical fiber connector are not ideal, resulting in direct contact between the two non-planar end faces of the connected optical fiber, leaving a certain gap or non-planar contact.

2. Production process control elements

(1) The quality of the ferrule

Mainly the inner diameter and concentricity of the ferrule. For multi-mode fiber optic connectors, the concentricity of the ferrule is required to be less than 3 microns, and for single-mode fiber optic connectors, the concentricity of the ferrule is required to be less than 1 micron. The concentricity of the ferrule, the physical parameters of the ground back, and the mating dimensions of the external parts all affect the concentricity of the core/ferrule, resulting in misalignment losses.

(2) Grinding degree

To measure the grinding quality, we must first look at the end face, and then look at the physical parameters. There are three main physical parameters: radius of curvature, spherical eccentricity, and fiber sag. For APC type connectors, there are two parameters of face angle (8 degree slope) and bond angle deviation. These parameters affect insertion loss.

(3) Size matching of external components

The dimensional fit of external components will directly affect the repeatability and interchangeability of the connector. Especially for APC type connectors, if the dimension fit is not ideal, the interchangeability and repeatability may exceed 0.1dB or worse.