Seven Professional Tests for Optical Transceiver

NADDOD Jason Data Center Architect Jan 18, 2023

There are many domestic optical module manufacturers, far more than most people imagine, and among them, more than 90% are small-scale, and some even say that they are small workshops.
Therefore, the optical modules circulating in the market are of different quality and uneven. When purchasing an optical module, especially a third-party optical module, you must ensure the compatibility of the optical module. Otherwise, it is very easy to encounter various problems, such as the more common ports are not up, link vibration, a large number of CRC error packets, packet loss, and the optical module is burned, the optical module is down while running, or the temperature of the network card is low. When the temperature rises, the optical module starts to lose packets. When a module is plugged in, many other ports nearby are down, and one end is UP and the other end is down, etc.

What Are the Differences Between Optical Modules From Different Manufacturers?

It is said that the standard of the optical module is very uniform, theoretically there should be no difference between the module manufacturers. But in fact, the reality is that the compatibility issues between different modules and different devices are all kinds of strange things, and even modules of the same model from the same manufacturer will have differences on the same device. There are many reasons, but if it is simply summarized, it is the difference between engineering quality and supply quality.
The quality of the PCB, the quality of the selected capacitors and resistors, the length and thickness of the gold fingers, the quality of the solder, and even the quality of the glue all affect the quality of the product. For example, if the voltage and current fluctuate and the temperature rises, problems will arise.
The difference in coupling process, such as COB coupling method, SMD coupling method, the choice of each manufacturer is different, even the choice of different products of the same manufacturer is also different, they will cause differences in cost, heat dissipation, and high temperature resistance.

Differences in production and testing equipment, the number of equipment, the richness of types, the degree of automation, and the richness of third-party equipment such as switches/server network cards will lead to differences in yield and compatibility.

Tests of NADDOD Optical Module

1. Average Output Optical Power Detection

The average output optical power is an important parameter of the optical module, which directly affect the communication quality. The NADDOD optical module measures the optical power output by the transmitting end of the optical module through an optical power meter, thereby completing the average output optical power test.

Output Optical Power Test

2. Extinction Ratio and Optical Modulation Amplitude (OMA) Test

The extinction ratio is one of the parameters used to measure the quality of the optical module. The test can detect whether the laser is working in the optimal bias point and optimal modulation efficiency range. In addition, optical modulation amplitude (OMA) is also a measure of the power difference when the laser is turned on and off. The two tests of the Nadode optical module were tested by mainstream optical oscilloscopes, and both passed the test.

Extinction Ratio

3. Bit Error Rate and Receiving Sensitivity Test

The bit error rate is one of the parameters to measure the ability of the optical module to transmit symbols correctly. The bit error rate test of Nadode optical module receives the optical signal with pseudo-random signal output by the tested optical module through the standard receiving tube test unit, and uses the standard receiving tube test unit to demodulate and compare to complete the bit error rate test.

Receive sensitivity is one of the key parameters to measure the performance of the receiving end device of the optical module. The receiving sensitivity test of Nadode optical module uses a programmable optical attenuation meter to attenuate the power of the signal, so that the signals of different powers received by the receiving end of the optical module are finally compared with the bit error rate under different optical power by the bit error meter. Complete the receiver sensitivity test.

4. Eye Diagram Test

Eye diagram testing and adjustment is an important stage to ensure that the optical module gets the best signal. The digital signal quality of the optical module can be seen from the eye diagram test results. The performance of the optical module can be judged by carefully observing the eye height, eye width, jitter, and duty cycle of the eye diagram. The larger the eye, the smaller the intersymbol interference. The performance of the optical module is better. The eye diagram test results of Nadod optical modules are very good, as shown in the figure below.

Eye Diagram Testing

5. Wavelength Test

Since the optical modules used on both ends of the equipment must emit the same wavelength to establish communication, so before shipment, the wavelength of the optical module of Nadod has been tested to ensure that it is within the deviation range. In addition, the Naduode optical module has also been tested for extremely low temperature, high and low temperature cycle test and constant humidity and heat test, all of which can work normally.

6. Aging Detection

Naduode optical module uses the light aging box to simulate the extreme conditions to test the optical module to verify whether the performance of the optical module meets the standard.

7. Real Machine Detection. <

Before shipment, the optical modules of Nadode have passed the actual test on the brand switch, and they can communicate normally.

Optical Module Tests

Whether it is the compatibility with the network card, the convenience of plug-and-play, the agility of one-stop communication, or the stability of network transmission, NADDOD optical modules can pass the test.