Cisco Cisco DWDM Transceiver Modules 白皮書
White Paper
© 2008 Cisco Systems, Inc. All rights reserved. This document is Cisco Public Information.
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OFL Bandwidth Test Setup: the Traditional Way
OFLBW is the originally standardized fiber bandwidth measurement method where the source
launches light uniformly into all modes of the multimode fiber. The launch condition of this
measurement is similar to that of an LED source. Therefore this measurement method gives a
good indication of system performance when using legacy protocols utilizing LED sources. Figure
3 depicts the OFL bandwidth measurement test setup defined by the FOTP-204 standard.
Figure 3. OFL Bandwidth Measurement Test Setup
Figure 4 depicts the results of the experiment conducted by the TIA FO-2.2.1 Task Group on
Modal Dependence of Bandwidth formed in 1996 to study the interaction between fiber and laser
source. It clearly shows the lack of correlation between advertised OFL bandwidth and the actual
fiber bandwidth measured for laser-based transmitters using the OFL characterization method.
Figure 4. Fiber Bandwidth Characterization for Laser Transmitters Using the OFLBW Measurement Method