In order to test the performance of a Fibre system several key measurements need to be carried out, these can include some or all of the following:
l End-to-end optical link loss
l Rate of attenuation per unit length
l Attenuation contribution of splices, connectors and couplers
l Length of the fibre or distance to an event
l Linearity of fibre loss per unit length
l Reflectance or optical return loss (ORL)
l Chromatic dispersion (CD)
l Polarisation Mode Dispersion (PMD)
l Attenuation Profile (AP)
Other measurements such as bandwidth may also be performed.
Some measurements require access to both ends of the fibre, such as Tier 1 optical loss testing, others require access to just one, such as Tier 2 testing with an OTDR.
Field Testing of Fibre cables falls into three group: installation, maintenance and fault finding/rectification.
The following provides a summary of each of these topics, the exact details of which depends upon the system design and the contractual requirements as outlined in the Systems Specification as detailed by the Client or their representatives.
Prior to installation, perform fibre inspections to ensure that the cables received conform to the right specifications of the project (Category, Length and Attenuation) Also ensure that all connectors, pigtails and couplers, meet the requirements along with the endface condition (particularly if pre-term assemblies have been supplied) have not been damaged in transit.
Installation and Commissioning Tests
During installation ensure that the area involved with the termination of the fibre is kept clean at all times and prevent the introduction of dust and debris, as this will have a major impact on the quality of system that will be handed over.Perform tests to determine the quality of cable splices and terminations including, end-face condition, attenuation, location and reflectance. Also carry out testing to ensure the installed system is suitable for the intended application. All these tests should be recorded and provided both to the customer as well as Excel Networking as part of the warranty application.
Maintenance testing involves periodic evaluation of the fibre cabling system to ensure that no degradation of the cable, splices or connections has occurred. The first stage of this should always be inspection of the end-face to ensure that no contamination has been introduced during the operation of the system. Other tests include cable attenuation along with attenuation and reflectance of splices and terminations.
It is the responsibility of the Client or their representatives to define the regularity of this testing.
Fault Finding and Rectification During fault finding and rectification perform testing to first identify the cause of the fault (transceiver, cable, connector, patch cord) as well as the location of the fault.
Once rectification has been successfully completed carry out testing of the repaired system following the guidelines covered in ‘Installation and Commissioning Test