• 1

How to achieve tens of kilometers of ultra-long distance transmission? By two small boxes? Quickly collect knowledge points!

When it comes to long-distance transmission, considering the cost, the old driver will first think of two things: fiber optic transceivers and bridges. With fiber optics, use transceivers. If there is no optical fiber, it depends on whether the actual environment can connect to the bridge.
More than ten kilometers and dozens of kilometers, but also to ensure stable and reliable transmission, optical fiber is imperative.
Today, let’s talk about the leading solution in optical fiber communication – optical fiber transceiver.
A transceiver is a device for signal conversion, usually referred to as a fiber optic transceiver. The emergence of optical fiber transceivers converts twisted pair electrical signals and optical signals to each other, ensuring smooth transmission of data packets between the two networks, and at the same time extending the transmission distance limit of the network from 100 meters of copper wires to 100 kilometers (single mode fiber).
With the continuous development of technology, it has become the current trend that high-speed serial VO technology replaces traditional parallel I/O technology. The fastest parallel bus interface speed is 133 MB/s of ATA7. The transfer rate provided by the SATA1.0 specification released in 2003 has reached 150 MB/s, and the theoretical speed of SATA3.0 has reached 600 MB/s. When the device works at high speed, the parallel bus is susceptible to interference and crosstalk, which makes the wiring quite complicated. The use of serial transceivers can simplify layout design and reduce the number of connectors. Serial interfaces also consume less power than parallel ports with the same bus bandwidth. And the working mode of the device is changed from parallel transmission to serial transmission, and the serial speed can be doubled as the frequency increases.
FPGA-based embedded Gb speed level and low-power architecture advantages, it enables designers to use efficient EDA tools to quickly solve the problem of protocol and speed changes. With the wide application of FPGA, the transceiver is integrated in FPGA, which has become an effective way to solve the problem of equipment transmission speed.
High-speed transceivers make it possible to transmit large amounts of data point-to-point. This serial communication technology makes full use of the channel capacity of the transmission medium and reduces the number of required transmission channels and device pins compared to parallel data buses, thereby greatly reducing communication. cost. A transceiver with excellent performance should have the advantages of low power consumption, small size, easy configuration, and high efficiency, so that it can be easily integrated into the bus system. In the high-speed serial data transmission protocol, the performance of the transceiver plays a decisive role in the transmission rate of the bus interface, and also affects the performance of the bus interface system to a certain extent. This research analyzes the realization of the high-speed transceiver module on the FPGA platform, and also provides a useful reference for the realization of various high-speed serial protocols.
This small box has a very high exposure rate in the long-distance transmission scheme, and can often be seen in our monitoring, wireless, optical fiber access and other scenarios.
how to use
Optical fiber transceivers are generally used in pairs, and are deployed at the access end (which can be connected to terminals such as cameras, APs, and PCs through switches) and the remote receiving end (such as computer room/central control room, etc., of course, it can also be used for access. terminal), thus building a low-latency, high-speed and stable communication bridge for both ends.
In principle, as long as the technical specifications such as rate, wavelength, fiber type (such as the same single-mode single-fiber product, or the same single-mode dual-fiber) are consistent, different brands are matched, and even one end of the fiber transceiver and one end of the optical module can be achieved. communication. But we don’t recommend it.
Single and Dual Fiber
The single-fiber transceiver adopts WDM (wavelength division multiplexing) technology, one end transmits wavelength 1550nm, receive wavelength 1310nm, and the other end transmits 1310nm and receives 1550nm, so as to realize data receiving and sending on one optical fiber.
Therefore, there is only one optical port on this type of transceiver, and the two ends are exactly the same. In order to distinguish, the products are generally identified by the A and B ends.
Single fiber transceiver (pictured is a pair, zero one)
The optical ports of the dual-fiber transceiver are “one pair” – the transmitting port marked with TX + the receiving port marked with RX, one end is a pair, and each sending and receiving performs their respective duties. The wavelengths of TX and RX are the same, both are 1310nm.
Dual-fiber transceiver (pictured is a pair, zero one)
At present, the mainstream single-fiber products on the market. In the case of comparable transmission capabilities, single-fiber transceivers that “save the cost of one fiber” are obviously more popular.

Singlemode and Multimode
The difference between single-mode optical fiber transceivers and multi-mode optical fiber transceivers is simple, that is, the difference between single-mode optical fiber and multi-mode optical fiber.
The core diameter of single-mode fiber is small (only one mode of light is allowed to propagate), the dispersion is small, and it is more anti-interference. The transmission distance is much higher than that of multi-mode fiber, which can reach more than 20 kilometers or even hundreds of kilometers. Usually applied within 2 kilometers.
That is precisely because the core diameter of single-mode fiber is small, the beam is difficult to control, and a higher-cost laser is required as the light source (multi-mode fiber generally uses LED light source), so the price is higher than that of multi-mode fiber, which is more cost-effective.
At present, there are many single-mode transceiver products on the market. Multi-mode data center applications are more, core equipment to core equipment, short-distance large-bandwidth communication.
three key parameters
1. Speed. There are Fast and Gigabit products available.
2. Transmission distance. There are products of several kilometers and dozens of kilometers. In addition to the distance between the two ends (optical cable distance), don’t forget to look at the distance from the electrical port to the switch. The shorter the better.
3. The mode type of the fiber. Single-mode or multi-mode, single-fiber or multi-fiber.

Post time: Mar-17-2022