Higher data rates
As telecoms networks have to carry more and more traffic to meet the demands of the Internet and other “Bandwidth Bandit” applications, then the data rates are getting higher and higher. 10Gb/s systems are being widely deployed and people are once again starting to talk seriously about 40Gb/s channels. The next development of Ethernet will include 100 Gb/s. At these very high data rates then many aspects of the fiber infrastructure become critical including chromatic dispersion and PMD (Polarization Mode Dispersion). Also the power budgets become much tighter so loss measurements are more critical.
Broader wavelength ranges
In addition to high data rates per channel, there is also a proliferation of multi-channel systems using DWDM technology – and as more channels are required and the data rates increase then the total grange of wavelengths being used also increases. CWDM (Coarse Wavelength Division Multiplexing) is also being deployed extensively in metro networks – this uses a very wide spread of wavelengths (ITU 6.694.2 mentions 1271 to 1 61 1 but notes that these end points are illustrative only).
Therefore the fiber might need to be characterized to assess its performance at wavelengths other than those it was originally intended for and tested against. For example OTDR testing at 1625nm to verify satisfactory operation at wavelengths beyond 1550nm.
Once the fiber infrastructure has been characterized then the performance attributes of particular links can be compared with the transmission requirements of any application standard to assess whether or not the link will support the application.
System selection or specification
The fiber characterization may also provide essential information that is needed for selecting or specifying the transmission equipment that will operate over the links.
There are now many choices to be made about different technology options for high performance telecoms systems. These different technologies can have quite different tolerance to various infrastructure impairments – knowing how good, or how bad, the infrastructure is can influence the choice of technology to be deployed.
Component quality checks
The presence of any defective components or problem areas in the infrastructure can be highlighted and recommendations made for any remedial work that needs to be carried out.