How to Test an SFP Transceiver

Fiber optical modules are extremely important in today’s optical fiber communication network. The development of data centers and cloud computing drive a large demand on the various rates of optical transceivers. However, the price of fiber optic transceivers is generally high offered by original equipment manufacturers (OEM) and brands, so many communication service providers favored third-party manufactures. Here comes the possible quality and performance issue when buying transceivers from a third-party supplier, so understanding how to test an optical transceiver is important. This post will introduce a performance testing system as the example of SFP transceivers of QSFPTEK, helping you get a full understanding of the optical transceiver testing procedure.

Working Principle of SFP Transceiver

Before introducing the testing system of the SFP transceiver, it is necessary to figure out its working principle. SFP transceiver is composed of optical components and functional circuits, which are designed for photoelectric conversion in optical fiber communication systems. The optical components include two parts of transmitting and receiving. On the transmitter (TX) side, the electrical signals are converted into optical signals and transmitted via a fiber link. Then on the receiver (RX) side, the received optical signals revert into electrical signals and transmit to switches and terminal routers. The working principle of the SFP transceiver is shown in figure 1.

Figure 1 - SFP Transceiver Working Principle

Figure 1 – SFP Transceiver Working Principle

Key Parameters to be Tested

The main testing parameters of the SFP transceiver can be analyzed from two aspects of transmitter parameters and receive parameters. The major transmitter parameters include transmit (Tx) power and the quality of the eye diagram. The major receive parameter is receiving sensitivity. Measuring the performance, judging if the transceivers are measuring up to the quality standards and working properly are largely based on these parameters. Next, the post will explain these parameters in detail.

SFP Transmit (Tx) Power Test

The Tx power is the signal level leaving from that device, which should be within the transmitter power range. For example, the transmit power range of SFP-10G-SR should be between -7.3dBm to -1dBm. Either the Tx power is higher or lower than the standard, the transceiver can’t work normally. The transmit power is an important parameter of the transmitter, which directly affects the communication quality of the transceiver. The transmit power is measured with the testing device of the optical power meter.

SFP Eye Diagram Test

The eye diagram of the SFP transceiver displays in the form of a waveform diagram to show the transmit performance of the SFP transceiver. The problems of ISI ( intersymbol interference) and noise can be found in the eye diagram, further, the quality of transmitting signals is able to be evaluated. More exactly, in the ideal case without ISI and noise, the waveform is shown as an open and big eye with a thin and clear outline. Moreover, if ISI exists, the eye will partly be closed and the outline of the eye will become blurred under the influence of noise. Figure 2 shows the eye diagram of the SFP transceiver with weak ISI and noise. The eye diagram is measured by the testing device of the Oscilloscope.

Figure 2 - Eye Diagram of SFP Transceiver

Figure 2 – Eye Diagram of SFP Transceiver

SFP Receiver Sensitivity Test

Receiver sensitivity is the other vital parameter for measuring the performance of the transceiver, which is defined as the minimum signal optical power level required at the receiver to achieve a certain BER performance. The noise at the receiving end of the SFP optical module is the main reason affecting the receiver sensitivity. The receiver sensitivity is measured by the testing device of Bit Error Rate Tester.

Automatic Test System of SFP Transceiver

QSFPTEK designed an Automatic Test System to improve the accuracy and efficiency of the testing process. All testing devices including optical power meter, Oscilloscope, and Bit Error Rate Tester are integrated and controlled by a computer. All the testing data will be saved in the database for the convenience of checking by the company engineers and customers. The Automatic Test System includes two platforms, transmit testing platform and receive testing platform, as shown in figure 3 and figure 4.

Figure 3 - SFP Transceiver Transmit Testing Platform

Figure 3 – SFP Transceiver Transmit Testing Platform

Figure 4 - SFP Transceiver Receiver Testing Platform

Figure 4 – SFP Transceiver Receiver Testing Platform


The mentioned above has explained the key parameters that need to be tested for transceiver modules and introduced an Automatic Test System of SFP transceivers designed by QSFPTEK. I hope the post is helpful for you when choosing quality assured and high-performance transceivers from third-party suppliers. By the way, with the professional and comprehensive Automatic Test System of QSFPTEK, it is believed that QSFPTEK is a reliable third-party supplier.

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