This part of IEC 62150 specifies test and measurement procedures for relative intensity noise (RIN). It applies to lasers, laser transmitters, and the transmitter portion of transceivers. This procedure examines whether the device or module satisfies the appropriate performance specification. The procedure is applicable to single longitudinal mode (SLM). An optional section of the procedure presents a controlled return loss to the device-under-test, but is only applicable to devices coupled to SMF.
The method described in this standard, using a time-domain detection system, provides a single value for RIN that averages the noise over the transmission bandwidth. The measurement is made on a modulated laser capturing the RIN value under normal operating conditions. It also measures RINOMA, an alternative definition, as described in IEEE 802.3-2005.
An alternative RIN measurement method uses a photoreceiver and electrical spectrum analyzer and provides RIN vs. electrical frequency. This method provides a RIN value averaged over particular electrical band determined by a filter. For a filter bandwidth and characteristic that duplicates the filtering in a transmission system, this technique provides a result that is appropriate to determine the noise for such a system.
This method is based on the measurement of total intensity noise including and does attempt to subtract the effects of thermal and shot noise.
Background on laser intensity noise is given in Annex A.