What are the criteria for judging the quality of communication optical fibers?

　　Judging the quality of communication fiber requires comprehensive evaluation from multiple dimensions such as physical characteristics, optical performance, connection quality and environmental adaptability. The following are specific judgment methods:

　　Physical inspection

　　Appearance damage

　　Check the fiber sheath for cracks, wear or extrusion deformation.

　　Observe whether the fiber is bent excessively (the bending radius should be greater than 20 times the diameter of the fiber, such as single-mode fiber recommended ≥ 30mm).

　　Verify that the connector (e.g. SC/LC/FC) is free from loosening, deformation, or corrosion.

　　End cleanliness

　　Use a fiber optic microscope or magnifying glass to observe the end face of the connector to ensure that there are no dust, scratches or oil stains.

　　Dirty end faces can lead to increased insertion loss and require special cleaning tools.

　　Second, optical performance testing

　　Attenuation test

　　Tools: Optical Power Meter + light source (such as red light pointer or laser light source).

　　Method:

　　The light source is connected at one end of the optical fiber, and the output optical power is measured with an optical power meter at the other end.

　　Compared with the theoretical attenuation value (e.g. single-mode fiber @1310nm wavelength attenuation of about 0.35dB/km), if the measured value is too high (e.g. more than 1dB/km), the fiber may be aged or damaged.

　　Reflection Loss (Return Loss) Testing

　　Tool: Optical Time Domain Reflectometer (OTDR).

　　Objective: To detect the reflected light intensity of the end face of the connector and reflect the polishing quality of the end face (e.g. the reflection loss of the APC end face should be ≥ 60dB).

　　Bandwidth and dispersion

　　Multimode fiber: Check the effective modal bandwidth (EMB) with a mode bandwidth tester to meet standards (e.g. OM4 ≥ 4700MHz · km).

　　Single-mode fiber: evaluate the dispersion coefficient through a dispersion tester (e.g. G.652 fiber @1550nm dispersion ≤ 18ps/(nm · km)).

　　III. Connector and wiring quality

　　Connector Type Matching

　　Verify the connector type (e.g. mixing SC/APC with SC/PC will result in increased reflection loss).

　　Check whether the adapter (flange) is compatible with the connector type (e.g. FC/APC adapter for single mode fiber).

　　wiring standardization

　　Avoid parallel wiring of optical fibers and power lines to prevent electromagnetic interference.

　　Make sure that the fiber reservation length is reasonable (it is recommended to reserve 1-2 meters in the cabinet) to avoid tension pulling.

　　IV. Environmental adaptability

　　Temperature and humidity

　　Check whether the fiber is exposed to high temperature (> 70 ° C) or high humidity (> 85% RH) for a long time, which may cause the jacket to age.

　　Outdoor optical fibers need to be resistant to ultraviolet light (UV) and hydrolysis.

　　mechanical stress

　　Verify whether the fiber cable is firmly fixed to avoid vibration or extrusion causing micro-bending losses.

　　Fifth, professional tool assistance

　　OTDR (Optical Time Domain Reflectometer): Aligned Bundle breakpoint, detect welding quality.

　　Fiber optic end face tester: Analyze connector end faces for scratches or contamination.

　　Insertion loss tester: Quickly measure the insertion loss and reflection loss of connectors.

　　summarize

　　If you lack professional tools, you can initially troubleshoot the fault through replacement methods (such as replacing fiber optic jumpers). For long-distance or high-speed networks (such as 10G/40G/100G), it is recommended to regularly use OTDR for full-link testing.