Principles and Scenarios of Optical Fiber Transceivers

The emergence of optical fiber transceivers perfectly realizes the seamless connection between optical cables and copper cables. It is often used in network applications that cannot be covered by the Ethernet copper network and must use optical fibers to extend the transmission distance. It has played a huge role in the domain network and the outer network.

What is a fiber optic transceiver?

Optical fiber transceivers are generally divided into two types, one is an Ethernet transmission media conversion unit that interchanges short-distance twisted-pair electrical signals and long-distance optical signals, usually called photoelectric converters; the other is After the optical signal is converted into an electrical signal, it is converted into another optical signal, also known as a fiber conversion repeater. The product is generally used in the actual network environment where the Ethernet cable cannot cover and must use optical fiber to extend the transmission distance, and is usually located in the access layer application of the broadband metropolitan area network; at the same time, it helps to connect the last mile of optical fiber to the metropolitan area. It also plays a huge role on the Internet and beyond.

How fiber transceivers access the network

Because the maximum transmission distance of the commonly used network cable (twisted pair) is very limited, the maximum transmission distance of the twisted pair is generally 100 meters. Therefore, when we are deploying a larger network, we have to use relay equipment. Of course, other types of lines can also be used for transmission, such as optical fiber is a good choice. The transmission distance of optical fiber is very long. Generally speaking, the transmission distance of single-mode fiber is more than 10 kilometers, and the transmission distance of multi-mode fiber can reach up to 2 kilometers. When using optical fibers, we often use optical fiber transceivers. At this time, the question arises, how to use the fiber optic transceiver? How does it connect to the network?

We all know that a network is composed of various optical devices, and fiber optic transceivers are an important part of them. When the optical fiber transceiver is connected to the network, the optical cable should be brought in from the outdoors first. The optical cable should be spliced ​​in the optical cable box, that is, the terminal box. The welding of optical cable is also a knowledge. It is necessary to strip the optical cable, splicing the thin fiber in the optical cable with the pigtail, and put it in the box after welding. The pigtail is to be pulled out, connected to the ODF (a kind of shelf, connected with a coupler), then connected to the jumper with the coupler, and finally the jumper is connected to the fiber optic transceiver. The next connection sequence is router----switch---LAN---host. In this way, the fiber optic transceiver is connected to the network.

Principle of Optical Fiber Transceiver

Types and applications of fiber optic transceivers

There are many types of fiber optic transceivers on the market today, but in general, there are two types of fiber optic transceivers used in the connection network between copper and fiber optic cables and fiber optic transceivers used in the connection network between fiber optic cables and fiber optic cables. These two types of fiber optic transceivers can be divided into different subcategories, and each category is described in detail below.

Fiber optic transceivers for copper and fiber optic connection networks

When the distance between two network devices exceeds the transmission distance of copper cables, fiber optic cables are required for connection, and fiber optic transceivers are responsible for the conversion between the two media. This fiber optic transceiver can be subdivided into the following categories:

1. Ethernet fiber optic transceiver

This type of fiber optic transceiver can connect devices used for Ethernet, Fast Ethernet and 10G Ethernet to achieve seamless connection between devices with different speeds and different port types. It is usually used for point-to-point transmission. Conversion, conversion of transfers on campus, etc. For example, when converting point-to-point transmission, two optical fiber transceivers can be used to connect two UTP (Unshielded Twisted Paired, unshielded twisted pair) Ethernet switches, or directly connect the UTP switch to an intelligent terminal.

2. TDM (Time Division Multiplexing, time division multiplexing) fiber optic transceivers

This type of fiber optic transceiver mainly has two types: T1/E1 and T3/E3. Both types of fiber optic transceivers need to be used in pairs, and can play a role in avoiding noise, improving service quality, and network security when extending cable transmission distances. T1/E1 fiber optic transceivers conform to T1 (1.544Mbps) and E1 (2.048Mbps) standards. For the installation and maintenance of T1 and E1 connection lines, these fiber optic transceivers can also play a role in testing and troubleshooting. T3/E3 fiber optic transceivers conform to T3 (44.736Mbps) and E3 (34.368Mbps) standards, and can be used to connect PBX (private branch exchange, private branch exchange), multiplexers and routers and other equipment. These fiber optic transceivers can be used for signal transmission between buildings and to extend telecommunication demarcation points.

3. Serial to fiber converter

This type of fiber optic transceiver is a multi-functional fiber optic MODEM that supports asynchronous RS-232, RS-485 communication interfaces, and is the best way to connect a remote terminal unit (RTU) to a host (HOST) or distributed data acquisition system (SCADA) controller. best choice. Support RS-232, RS-485 multiple asynchronous communication protocols, can mix two RS-232, RS-485 interfaces at the same time, support 2-wire (half-duplex) RS-485 working mode.

The RS-485 fiber optic transceiver supports data (TXD or SD) transmission control, thereby improving the ability to adapt to various software and simplifying the control method. The fiber optic MODEM supports a variety of fiber optic connection methods between asynchronous serial ports. It supports The devices with two asynchronous serial ports carry out full-duplex or half-duplex communication through optical fiber, and the communication distance can reach up to 4 kilometers for multi-mode and 20 kilometers for single-mode. The signal transmission rate of 485 can reach up to 460Kbps, and the interfaces of different electrical standards can be mixed. RS-232 equipment can be used to connect RS-485 equipment, which can replace RS-232 to RS-485 interface converter or optoelectronic isolator , and provides excellent EMI/RFT (electromagnetic interference/functional test) characteristics.

Optical transceivers for connecting networks between optical cables

This type of fiber optic transceiver can support the connection between single-mode and multi-mode fibers, simplex and multiplex fibers, and convert optical and electrical signals. Specifically, it is divided into multi-mode to single-mode optical fiber transceivers, duplex to simplex optical fiber transceivers, and SFP band conversion transceivers.

1. Multi-mode to single-mode fiber optic transceiver

In the signal transmission of the enterprise network, sometimes the transmitting end may use a multi-mode device, while the party receiving the signal uses a single-mode device. In this case, a multi-mode to single-mode fiber optic transceiver can be used for Conversion of multimode fiber to single mode fiber. In addition, the use of multi-mode to single-mode optical fiber transceivers can better meet the needs of long-distance transmission, with a maximum transmission distance of up to 140km, which can meet the requirements of low cost and high connectivity at the same time. In the figure below, two Ethernet switches with multi-mode ports are connected to two fiber optic transceivers respectively to convert multi-mode to single-mode for long-distance transmission.

2. Duplex to simplex fiber optic transceiver

Sometimes, the transmission of enterprise network also needs to convert duplex fiber to simplex fiber, which mainly depends on the number of fibers in the transceiver equipment. As the name implies, the data received and sent by a single-fiber fiber is transmitted on one fiber, and the data received and sent by a dual-fiber fiber is transmitted on a pair of fibers. Single-fiber equipment can save half of the optical fibers, that is, data reception and transmission can be realized on one optical fiber, which is very suitable for places where optical fiber resources are scarce. This type of product adopts the technology of wavelength division multiplexing, and the wavelengths used are mostly 1310nm and 1550nm. One of the two ports of the optical fiber transceiver in the figure below is single-fiber and the other is dual-fiber, which realizes the conversion from dual-fiber to single-fiber.

3. Band conversion transceiver

The biggest feature of the WDM Optical Amplifier Repeater (OEO) series is that it can receive, amplify and retransmit signals through different wavelengths without changing the data/signal content. Today, wavelength conversion can only be achieved through the WDM Optical Amplifier Repeater Series (OEO). The WDM Optical Amplified Repeater Series (OEO) works like a regenerator, converting an optical input signal to an electrical signal, passing a new electrical pulse amplitude and waveform, generating a logical copy of the input signal, and using this electrical signal to drive The transmitter produces an optical signal with a new wavelength.

concluding remarks

Optical fiber transceivers can support a variety of protocols, transmission rates and transmission media. While it truly achieves non-blocking transmission switching performance, it also provides functions such as balancing traffic, isolating conflicts and detecting errors, ensuring high security and safety during data transmission. stability. It can be predicted that fiber optic transceivers will be active in network deployment for a long time in the future, and are an indispensable part of actual network formation.