High-quality optical module distinction

The quality of the optical module determines the network transmission performance, once the workload is reduced, the performance will be greatly reduced.

Like other high-tech equipment, optical transceivers also go through strict testing and quality inspection procedures during the manufacturing process, such as optical power testing, sensitivity testing, eye diagram testing, burn-in testing, real machine testing, fiber end-face testing, etc. . These processes touch every stage of the production process to ensure the best possible results. If any procedure fails, the optical module is rejected and returned to the production line for the heavy lifting. So how to test the performance parameters of the optical module?

Optical module average output optical power measurement

The launch port of the optical module is composed of a light source and related electronic circuits. Semiconductor-based light-emitting diodes (LEDs) and laser diodes are used as light sources in optical transistors. LEDs and vertical cavity surface emitting lasers (VCSELs) are commonly used as transmitters on local and local networks, while Fabry-Perot (FP) lasers and distributed feedback (DFB) lasers are used in metro and long-haul networks in the transmitter.

optical module

In optical communications, the light source is intensity modulated, which is the process of applying a varying current to the laser to vary the output power level. As shown in Figure 1, limited power levels represent logic zeros, rather than true no power at all.

The average output optical power is an important parameter of the transmitter, which directly affects the communication quality of the module. It is the average optical power of the receiver under normal operating conditions. The optical power meter can test the optical power at the transmission end by measuring the average output optical power. For transmitters used for long-distance transmission, the average optical power is greater than the maximum input optical power.

Measure the average optical power with an optical power meter. The unit of measurement is usually expressed in dBm, which is the logarithmic ratio of the power level to 1mW.

Optical Power Meter

Optical module extinction ratio measurement

When the extinction ratio is used to describe the performance of an optical transmitter used in digital communications, its extinction ratio is the energy (power) used to transmit a logic level "1" to the energy used to transmit a logic level "1" Compare. 0”. For a graphical description, an eye diagram is usually used, as shown in Figure 2.

Optical Modulation Amplitude Measurement

Optical modulation amplitude (OMA) is used to measure the difference between two optical power levels produced by a power supply, such as P1 (when the light source is on) and P0 (when the light source is off). For OMA, low or high drop ratios can be used as long as the transmitter is eye-safe and does not overload the receiver.

Receiver Sensitivity Test

Receiving sensitivity is one of the key parameters to measure the performance of optical module receiving equipment. The receiving sensitivity test needs to attenuate the power of the signal through the programmable optical attenuator, and the error rate of different optical power can be compared by the error meter to complete the optical module receiving different power signals. Wherein, the better the receiving sensitivity is, the smaller the minimum received optical power is. Conversely, if the receiving sensitivity is poor, the requirements for the optical receiver will be higher.

Optical module eye diagram test

An eye diagram is a common tool for viewing the output of a transmitter. It provides a lot of information about the overall performance of the transmitter. In an eye diagram, all combinations of data patterns are superimposed on a common timeline, typically less than a two-bit period. Figure 1 shows a signal with good amplitude and low jitter. You can imagine the way an eye diagram is constructed by drawing eight possible sequences of 8 three-bit waveforms (000,001,...110,111) overlapping on a common timeline.