Home Tech How a 40G QSFP+ Transceiver Works

How a 40G QSFP+ Transceiver Works

by Adam Smith
Transceiver Works

At present, the demand for bandwidth is becoming higher and higher, and the demand for high-capacity optical communication equipment is also becoming more and more urgent. Therefore, the optical transceiver, as the key part of optical communication equipment, is becoming more and more popular and the rate is becoming higher and higher. 

The four-channel 40G QSFP+ optical module is specially designed for the needs of high density, high speed, and hot-pluggable. QSFP+ optical module, whose total data transmission speed of four channels reaches 40Gbps, is located in the physical media-related layer in the optical fiber communication Ethernet protocol. It is the core component for photoelectric and electro-optic conversion. The 40G QSFP+ optical transceiver can be adjusted to different transmission speeds and can be applicable to Ethernet, Fiber Channel, and Infiniband standards to solve data transmission with high efficiency. This article will give a comprehensive introduction to how a 40G QSFP+ transceiver works.

QSFPTEK Cisco Compatible 40GBASE-SR4 Transcevier

Working Principle of 40G QSFP+ Optical Module

It is equivalent to the communication between optical modules in the whole system. The principle of the optical module is to realize the interconnection of high-speed electrical signals by using the photoelectric conversion and electro-optical conversion functions of the optical module. The intermediate transmission uses light to transmit in the optical fiber. Therefore, on the same line, the function of the optical module at one end is photoelectric conversion to convert the optical signal into the corresponding high-speed electrical signal, while the other end is exactly the reverse process of the above photoelectric conversion, electro-optical conversion, that is, the high-speed electrical signal is modulated into an optical signal and transmitted. The optical module has become an indispensable part of high-speed optical network communication. It is mainly used in the fields of the data center, the interconnection between servers, and so on.

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The 40G QSFP+ optical module is mainly composed of the main control chip, 4-channel VCSEL laser driving chip, 4-channel VCSEL laser, 4-channel pin detection chip, 4-channel pin detection chip driving chip, and optical and electrical interfaces. The basic principle block diagram is shown in the figure below.

40G QSFP+ Working Principle Diagram

The working process of the 40G QSFP+ optical module is to input 4-channel electrical signals with a rate of up to 10Gbps to the driving chip of 4-channel VCSEL laser through the electrical interface. The main control chip exchanges data with the electrical interface using I2C pin, and then the main control chip configures the driving chip of 4-channel VCSEL laser, The driving chip of the 4-channel VCSEL laser can drive the 4-channel VCSEL laser array normally, so that the 4-channel VCSEL laser can emit the corresponding modulated optical signal. Through the transmission of optical interface and optical fiber, the optical signal is coupled into the 4-channel pin detector through the optical interface. At the same time, the main control chip exchanges the data of I2C protocol with the electrical interface, controls the 4-channel pin detector driving chip to drive the 4-channel pin detector, converts the optical signal into a high-speed electrical signal at the corresponding rate, and finally outputs it through the electrical interface. That is, the conversion from electrical signal to optical signal is realized by VCSEL laser, and the conversion from optical signal to electrical signal is realized by pin detector.

Composition of 40G QSFP+ Optical Module

Transmitter Part Composition 

The optical emission part of the 40G QSFP+ optical module is mainly composed of an electrical interface, main control chip, 4-channel VCSEL laser driving chip and 4-channel VCSEL laser, which plays the role of electro-optical conversion. The basic principle block diagram of the light emitting part of the 40G QSFP+ optical module is shown in the figure below.

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40G QSFP+ Transceiver Transmitter Principle Diagram

The main working process of the optical emission part is that four parallel 10Gbps high-speed differential electrical signals enter the 40G QSFP+ optical module through the electrical interface, and then enter the VCSEL laser driving chip. At the same time, the main chip communicates with the electrical interface for I2C, and controls the VCSEL laser driving chip to drive the four channel VCSEL laser, so that the VCSEL laser sends out the corresponding modulated light output. The main working principle of the 40G QSFP+ optical module studied in this paper is the mutual conversion between four channels of electrical signals up to 10Gbps and optical signals, which is mainly used in short-distance transmission. It belongs to the 40G QSFP+ SR4 series. Therefore, the VCSEL array has 4 parallel transmission channels.

Receiver Part Composition

The light receiving part of the 40G QSFP+ optical module is mainly composed of an electrical interface, main control chip, driving chip of 4-channel pin detector and 4-channel pin detector for photoelectric conversion. The basic principle block diagram of the light receiving part of the 40G QSFP+ optical module is shown in the figure below.

40G QSFP+ Transceiver Receiver Principle Diagram

The main working process of the optical receiving part is that four parallel optical signals enter the 40G QSFP+ optical module through the four channel pin detector array, and then enter the pin detector array driving chip. At the same time, the main chip communicates with the electrical interface for I2C and controls the driving chip of the pin detector array to drive the four channel pin detector array to work normally. Make the driving chip of the pin detector array send out corresponding 4-channel parallel electrical signal output.

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Conclusion

This paper mainly studies the principle design of the 40G QSFP+ optical module. The principle of the 40G QSFP+ optical module is analyzed, and the composition of the transmitting part and receiving part of the module is introduced in detail. QSFPTEK offers a full range of 40G QSFP+ products,including 40G QSFP+ SR4, 40G QSFP+ LR4, 40G QSFP+ ER4. Welcome to consult via [email protected]

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