Specifications

4-10
Cisco ONS 15530 Planning Guide
OL-7708-01
Chapter 4 Optical Loss Budgets
Fiber Plant Testing
Fiber Plant Testing
Verifying fiber characteristics to qualify the fiber in the network requires proper testing. This document
describes the test requirements but not the actual procedures. After finishing the test measurements,
compare the measurements with the specifications from the manufacturer, and determine whether the
fiber supports your system requirements or whether changes to the network are necessary.
This test measurement data can also be used to determine whether your network can support higher
bandwidth services such as 10 Gigabit Ethernet, and can help determine network requirements for
dispersion compensator modules or amplifiers.
The test measurement results must be documented and referred to during acceptance testing of a
network.
Fiber optic testing procedures must be performed to measure the following parameters:
• Link loss (attenuation)
• ORL (optical return loss)
• PMD (polarization mode dispersion)
• Chromatic dispersion
Link Loss (Attenuation)
Testing for link loss, or attenuation, verifies whether fiber spans meet loss budget requirements.
Attenuation includes intrinsic fiber loss, losses associated with connectors and splices, and bending
losses due to cabling and installation. An OTDR (optical time domain reflector/reflectometer) is used
when a comprehensive accounting of these losses is required. The OTDR sends a laser pulse through
each fiber; both directions of the fiber are tested at 1310 nm and 1550 nm wavelengths.
OTDRs also provide information about fiber uniformity, splice characteristics, and total link distance.
For the most accurate loss test measurements, an LTS (loss test set) that consists of a calibrated optical
source and detector is used. However, the LTS does not provide information about the various
contributions (including contributions related to splice and fiber) to the total link loss calculation.
A combination of OTDR and LTS tests is needed for accurate documentation of the fiber facilities being
tested. In cases where the fiber is very old, testing loss as a function of wavelength (also called spectral
attenuation) might be necessary. This is particularly important for qualifying the fiber for
multiwavelength operation. Portable chromatic dispersion measurement systems often include an
optional spectral attenuation measurement.
SDI 17 20
DVB-ASI 9 11
Table 4-13 Latency Values for 8-Port Multi-Service Muxponders (continued)
Protocol
Unidirectional End-to-End Latency for 0 km Fiber
Typical Latency
(microseconds)
Maximum Latency
(microseconds)