The test of an an SFP+ transceiver module can be divided into two parts: the transmitter testing and the receiver testing.
SFP+ Transmitter Testing
SFP+ transmitter parameters may include wavelength and shape of the output waveform. There are two steps to test a transmitter:
1. The input signal used to test the transmitter must be good enough. Measurements of jitter and an eye mask test must be performed to confirm the quality using electrical measurements. An eye mask test is the common method to view the transmitter waveform and provides a wealth of information about overall transmitter performance.
2. The optical output of the transmitter must be tested using several optical quality metrics such as a mask test, OMA (optical modulation amplitude), and Extinction Ratio.
SFP+ Receiver Testing
SFP+ receiver may specify tolerance to jitter and bandwidth. To test a receiver, there are also two steps:
1. Unlike testing the transmitter, where one must ensure that the input signal is of good enough quality, testing the receiver involves sending in a signal that is of poor enough quality. To do this, a stressed eye representing the worst case signal shall be created. This is an optical signal, and must be calibrated using jitter and optical power measurements.
2. Then, testing the electrical output of the receiver must be performed, which includes three basic categories of tests:
- A mask test, which ensures a large enough eye opening. The mask test is usually accompanied by a BER (bit error ratio) depth.
- Jitter budget test, which tests for the amount of certain types of jitter.
- Jitter tracking and tolerance, which tests the ability of the internal clock recovery circuit to track jitter within its loop bandwidth.