Optical Fiber Link Test Solution

1. Overview

Fiber is the best transmit medium ever before with such a great many advantages: large available bandwidth, high quality transmission, long- distant transmission, strong anti-jamming capability, high network reliability, saving channel sources and without interfered to each other. However, an integrated fiber link does not lie on its quality but also the quality of joints, workmanship and field condition. So fiber link field test is very important.

Fiber link field test is a necessary part of installation and maintenance fiber network which aims to locate the trouble reasons through testing the fiber link quality per special standard and reducing trouble points. 

Finger 1 Fiber Network

2. Test Contents

1) Power Meter Test

Power Meter, the basic fiber project test, could validate the transmission signal intension .Put power meter at one end and optical resources at another end during test. OPWILL Fiber Link series product OTP6122 can supply most accurate power meter tests.

2) Insert Loss Test

Insert Loss, used to test the attenuation of some part fiber link, is one of Insert Loss tests, including fiber cable loss, joint loss, fusion splices loss and etc.

Insert loss test can validate the installation of fiber and linker right or not. The method of inserting loss is to test the intension of from end to end through power meter.

OPWILL fiber link series product OTP6122 offers steady laser sources and supports both 1310mm and 1550mm wavelength.  

In actual fiber cable project, it needs bi-directional insertion loss measurement.

Finger 2 Bi-directional Insertion Loss Measurement

          OTP6122 supports test information communication through optical cable at optical source and power meter ends in order to get insertion loss results at single side directly.

Finger 3 Single direction Insertion Loss Measurement


3) VFL

VFL could identify fiber breakpoint, macrobend and achieve end to end fiber identification by using 650nm laser visual   power to test single port and multi ports short distant fiber troubleshooting.

         OPWILL fiber link product OTP6122 could supply 650nm glow VFL function.

4) ORL

One part of the dispersion and reverberation during optical pulse transmission caused by the features, connectors, jointers, bends something like these of fiber will return to fiber and it will interrupt the optical signal, especially for poor cleanliness of fiber connectors, macrobend, bad fiber connectivity.

Opwill fiber link series OTP6122 offer ORL function.


EVOA is mainly used for reducing and controlling optical signals through supplying stable and changeable optical attenuator to simulate real optical cable attenuation.

OPWILL fiber link series OTP-60V could realize power and attenuation test with OTP6122.

Finger 4 EVOA Test


It needs final test after optical link project to record optical link length, link loss, joint loss, optical cable length, series of joints positions and loss information which could be referred to in the following acceptance and maintenance.

The common tool for optical cable is OTDR which adopts time domain measurement by sending optical pulse to the tested optical fiber and through returned Rayleigh scattering and Fresnel reflection optical signal distribution in optical fiber to protract OTDR curve to test optical cable attenuation, connector loss, optical fiber trouble point location and optical cable loss distribution.  

Finger 5 OTDR Curve

Optical cable link loss estimation:

It is necessary to estimate the optical cable link loss before construction. One integrated optical fiber link includes optical fiber, linker and fusion splices so it needs to consider optical fiber loss itself, linker loss and fusion splices loss when estimate the loss of optical cable link.

Fiber optical link attenuation=optical fiber attenuation+ linker attenuation+ fusion splices attenuation

Optical fiber attenuation=optical fiber attenuationdB/km×optical fiber length (km)

Linker attenuation=linker attenuation/unit × linker number

         Fusion splices attenuation=fusion splice attenuation/unit× fusion splice number 

Finger 6 Optical fiber attenuation

          If metrical attenuation is bigger than estimation after construction, it needs OTDR to    locate the trouble point and find out the reasons. For example, there is a fusion splice at the front 1000m in poor quality which is over 2dB.Users can locate all the poor adapters, fusion splices, optical fiber breakpoint and end and etc through OTDR.  

OPWILL’s OTDR series of products contain high dynamic range OTM2300 and portable low dynamic range OTP6123.OTDR optical cable test curve as following:

Finger 7 OTDR Curve


3. How to use OTDR correctly

1) Setup correct OTDR parameters

Setup following parameters before testing:

A.        Optical fiber refractive index of tested optical cable

B.        Test wavelength

C.       Pulse width

D.       Sampling time

E.        Test distance range

Users can choose intelligent measurement under unknown optical cable length condition. OTDR will detect general length of optical cable automatically and setup proper parameters for test.

Finger 8 Setup OTDR parameters


2) OTDR Curve Analysis

OTDR could analyze optical cable different kinds of events and exact loss information through Curve Analysis Function including moving Ruler (AB line), zooming in and out of the curve and analyzing events and curve information automatically.

Finger 9 Setup OTDR Curve Analyze

3) OTDR Curve Common Event Type

A. Reverberation Event

Finger 10 OTDR Reverberation Event

         It shows top mutation in the optical cable curve which are formed by sudden breaks of refractive index.

B. Non-reverberation Event

Finger 11 OTDR Non-reverberation Event

          It is caused by fusion splices, macro bend or micro bend in the optical cable without obvious mutation.

CTop and end of optical cable

The top of OTDR curve optical fiber is optical cable beginning event. Generally, the top of optical cable locates at the first tested event (the first linker of OTDR).

The end of OTDR curve optical fiber is optical cable end event. Generally, the end of optical fiber locates at the last tested event which is called as optical cable end event.


4) Fast way to search faults among many optical cables

OPWILL OTDR supports real time test module in which sampling time is 1s and user could update the curve instantaneously and insert and pull out the optical fiber to do test among several optical cables to remove the troubles rapidly.


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