Testing C37.94

C37.94 Testing is an optional feature and it must be activated in order to have access to its functions.

The C37.94 optical data rate is very low by today’s standards and not all modern SFPs are compatible with it (most are designed for rates ≥ 100 Mbit/s). Only use SFPs recommended by VeEX, which have are non-blocking and have a clock and data recovery (CDR) capable of working at 2048 kbit/s.

The output signal of modern 850nm SFP modules is stronger than the original standard teleprotection equipment input range. To avoid saturation or invalid measurements, use an optical loopback cord to measure the actual SFP output power. Then add the appropriate in-line attenuator, in the TX direction, to match network elements’ output, if necessary (e.g. 5 or 10 dB). Although some modern C37.94 equipment can accept higher power inputs, the original IEEE standard refers to a maximum of -11 dBm output at the TX port. The original dynamic range at the RX was defined as -32 to -11 dBm.

Although C37.94 defines an optical interface operating at 830 ±40 nm over multi-mode fiber (MMF) with BFOC/2.5 (ST) connector, it is not uncommon today to find implementations running at 1310 nm MMF or SMF, for longer reach or to reuse existing SMF fiber used for other telecommunication purposes. Common fiber optics connectors or adapters, other than BFOC, may also be found in the field.