The components of the SFP+ optical transceiver module mainly include optical signal input interface, receiver (Receiver), transmitter (Transmitter), integrated circuit design (IC Design), radio frequency circuit (RF circuit), digital monitoring (Digital Control) ), mechanical support part. SFP optical transceiver modules mainly have the following features: dual LC connection, support for hot-swap, can effectively avoid electromagnetic interference (EMI), and very good electrostatic protection ability (ESD).
The internal block diagram of the SFP+ optical module is shown in the following figure:
At the SFP+ laser output end, the electrical signal is input through the Tx Data end of the module to drive the FP (factor pluggable transceiver)/DFP (factor pluggable transceiver) laser to output the optical signal; at the receiving end, the optical signal passes through the PIN (factor pluggable transceiver)/ The APD (factor pluggable transceiver) detector is converted into an electrical signal, and the current is converted into a voltage through the trans-impedance amplifier TIA (Transimpedance Amplifier), and then passed through the low-pass filter LP (low-pass) Filter and then passed through the radio frequency amplification limiter RF AMP ( radio frequency amplifier) Limiter output electrical signal.
The main components of SFP+ optical modules are:
(1) Optical component OSA (Optical Sub-system Assembly)
It is a combination of optical devices (for example, the internal structure of ROSA has PIN-TIA and APD-TIA, etc.), and it is divided into the following categories:
TOSA (Transmitter OSA): It mainly converts a given electrical signal to an optical signal, and sends the converted optical signal. It plays an important role in the luminous efficiency, average output optical power, and optical port eye diagram of
the product. effect;
ROSA (Receiver OSA): It mainly accepts a given optical signal and converts the electrical signal, and outputs the electrical signal to the receiver circuit at the same time. It plays an important role in the overload, receiving sensitivity, dynamic range, electrical eye diagram of the product, etc. the role of;
BOSA (Bi-directional OSA): It includes all the performances and functions of TOSA and ROSA. It is an optical component that integrates transceivers, and it also has special requirements that transceivers do not interfere with each other.
(2) Working circuit part PCBA:
This part plays a vital role in the normal operation of the product, and it is also the part with the highest probability of failure of the product. We can also divide it into several key working circuits:
Drive circuit – mainly provides a suitable bias and modulation current for the laser, so that the laser can emit light normally, and at the same time can transmit the optical signal normally. Its key components are the laser driver and related peripheral circuits, such as high-speed data transmission circuits. The circuit directly determines the output optical power, extinction ratio and optical port eye diagram of the module;
Amplifier circuit – mainly amplifies the electrical signal output by ROSA according to a certain amplitude, and transmits it to the data processing system, and at the same time judges the valid/invalid limit of the input optical power (the control is supported by the corresponding peripheral circuit). Its key component is the limiting amplifier, which directly affects the module’s sensitivity, LOSA/LOSD range, electrical port eye diagram, etc.;
Monitoring/tuning circuit—mainly monitor the information of the module EEPROM, such as the monitoring of the working current, voltage, temperature, output optical power, input optical power, etc. of the product. Secondly, adjust the relevant parameters of the product, such as the output optical power, extinction ratio, APD high voltage, LOSA/LOSD range, etc. of the product. Its key device is a monitoring chip, such as DS1856, ADUC7020, etc., and it also has the function of digital potentiometer.
The related research on high-speed optical modules has attracted extensive attention. The 100GBASE-LR4 Ethernet transceiver proposes a compact 4×25Gb/s ROSA (Receiver Optical Sub-system Assembly) module with a large alignment tolerance structure and high receive sensitivity, using optical DMUX-based thin-film filters and Double lens (collimating and focusing lens) system, in order to save space and reduce volume, by changing the electrical signal path by 90 degrees, the butt coupling structure in silicon AWG and four PD chips forms a high-speed electrical transmission line on the side of the ceramic substrate The method constitutes a compact 4×25Gb/s optical transceiver module, and the receiving sensitivity of the four channels is less than -11.5 dBm.