Fiber Optic Transceiver Testing Guide

In fiber optic network, the normal operation of fiber optic links is of great importance for the entire system which should work smoothly. So, once the fiber optic transceiver is deployed for fiber optic links, to test the performance of it is the primary task. Although in today’s data centers, the fiber optic transceivers used may be offered by different suppliers, proper compliance testing on fiber optic transceivers is still needed to ensure that system-level specifications are met when all components are connected. Do you know how to test the compatibility and interoperability of fiber optic transceiver? The following paragraphs give you the answer.

Fiber Optic Transceiver Basics

There are several types of fiber optic transceiver available in telecommunication market for many applications at different Gigabit data rates: such as SFP (eg.GLC-SX-MM), SFP+, 40G QSFP+ 100G CFP, etc. A fiber optic transceiver consists of a transmitter and a receiver. The transmitter takes an electrical input and converts it to an optical output from a laser diode or LED. The light from the transmitter is coupled into the fiber with a connector and is transmitted through the fiber optic cable plant. The light from the end of the fiber is coupled to a receiver where a detector converts the light into an electrical signal which is then conditioned properly for use by the receiving equipment.

When a transmitter is paired with a receiver through a fiber and the desired bit-error-ratio (BER) is not achieved, is the transmitter at fault? Or, is it the receiver? Perhaps both are faulty. A receiver of low quality can be compensated for by a high-performance transmitter or vice versa. As such, specifications are put forward so that any receiver will interoperate with the worst-case allowable transmitter, and any transmitter will provide a signal with sufficient quality so that it will interoperate with the worst-case allowable receiver.

Fiber Optic Transceiver Testing

Generally speaking, there are four basic steps taken to test the fiber optic transceiver, transmitter testing and receiver testing.

Transmitter Testing

Transmitter testing factors include wavelength and shape of the output waveform. Two steps are followed to test the transmitter:

First, the input signal used to test the transmitter must be of high quality. 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.

Second, 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.

Receiver Testing

Similarly, the are also two steps to test the receiver:

Unlike transmitter testing, where the designer must ensure that the input signal is of sufficient quality, receiver testing involves sending in a signal that is of poor quality. To do this, a stressed eye is created to represent the worst-case signal. Then using jitter and optical power measurements to calibrate this optical signal.

The last step is to test the electrical output of the receiver, which uses three basic categories of tests. Here goes a mask test to ensure a large-enough eye opening, a jitter-budget test that tests for the amount of certain types of jitter, and jitter tracking and tolerance to determine the ability of the internal clock-recovery circuit to track jitter within its loop bandwidth.

Conclusion

In a word, fiber optic transceiver testing seems to be a complicated task, but this process holds an important position in the whole system. Fiberstore offers all kinds of transceivers which are fully compatible with major brands, like Cisco (eg.SFP-GE-L), HP, Juniper, etc. They are all test-assured, sold at reasonable prices. For more information about fiber optic transceivers, you can visit Fiberstore.