Optical fiber, light module and light interface common knowledge in weak electricity engineering

Optical fiber, light module and light interface common knowledge in weak electricity engineering

This article shares the common knowledge of fiber, optical modules, and optical interfaces. I hope it will be helpful to everyone.

The light modules commonly used in the Ethernet switch include SFP, GBIC, XFP, XenPak.

Their English name:

Sfp: Small Form-FactorPluggabletransceiver, small encapsulation

GBIC: Gigabit InterfaceConverter, Gigabit Ethernet interface converter


Small packaging can be inserted and removed

Xenpak: 10-Gigabit EthernettransceiverPackage Metaidae Terrier Sendor Collection Package.

The optical fiber connector

The optical fiber connector consists of a plug at both ends of the fiber and the optical fiber. According to different locking mechanisms, fiber -fiber connectors can be divided into FC, SC, LC type, ST type and KTRJ type.

The FC connector uses a thread lock mechanism. It is an optical fiber activity connector that has been invented earlier and used the most.

SC is a rectangular connector. It is developed by NTT. It can be plugged directly and plugged directly. Compared with the FC connector, it has a small operating space and easy to use. Low -end Ethernet products are very common.

LC is a MINI -type SC connector developed by Lucent. It has a smaller volume and is widely used in the system. It is a direction for the development of fiber optic activity connectors in the future. Low -end Ethernet products are very common.

The ST connector is developed by AT & T. It is locked by a card mouth -type locking mechanism. The main parameter indicators are equal to the FC and SC connectors, but the application of the company is not common. It is usually used in multi -mode device connections. It is equipped with other manufacturers. Use more during docking.

KTRJ’s pins are plastic. Through steel needle positioning, as the number of insertions increases, each cooperative surface will wear, and the long -term stability is not as good as the ceramic needle connector.

Fiber knowledge

Optical fiber is a conductor that transmits light waves. Fiber can be divided into single -mode fiber and multi -mode fiber from the mode of optical transmission.

In the single -mode optical fiber, there is only one type of base mode, which means that the light is transmitted only along the core of the fiber. Due to the completely avoided mode scattering, the transmission band of the single -mode fiber is very wide, so it is applicable and high -speed, and the long -distance fiber is generally accepted.

There are multiple modes in the light transmission in multi -mode fiber. Due to the scattered or simidities, the transmission performance of this fiber is poor, the frequency band is narrow, the transmission rate is small, and the distance is short.

Fiber characteristic parameters

The pre -made quartz fiber rod of the optical fiber is made. The outer diameter of the multi -mode fiber and single -mode fiber for communication is 125 μm.

The slim body is divided into two areas: the core (Core) and the Cladding Layer. The diameter of the single -mode fiber fiber fiber is 8 ~ 10 μm, and the multi -mode fiber fiber core diameter has two standard specifications. The core diameter is 62.5 μm (US standard) and 50 μm (European standard).

The interface optical fiber specifications have such descriptions: 62.5 μm/125 μm multi -mode optical fiber, of which 62.5 μm refers to the core diameter of the fiber, and 125 μm refers to the outer diameter of the fiber.

The light wavelength used in single -mode optical fiber is 1310nm or 1550 nm.

Most of the light waves used in multi -mode optical fiber are 850 nm.

In terms of color, you can distinguish single -mode fiber and multi -mode fiber. The single -mode fiber outer body is yellow, and the multi -mode fiber outer body is orange -red.

Gigabit light

Gigabit light can work in two modes: compulsory and self -negotiating. 802.3 Gigabit light port only supports 1000M rate, and supports two dual -workers (FULL) and Half.

The most fundamental difference between self -negotiation and compulsory is the different code flow sent when the two establish a physical link. The self -negotiating mode sends/C/code, that is, the configuration code flow, and the mandatory mode is sent// I/code, that is, idle code flow.

Gigabit light mouth self -negotiation process

1. Both ends are set to self -negotiating mode

The two parties send each other/C/code flow. If the three of the same/C/code are continuously received and the code flow received by the receiving method is matched with the local working method, it is returned to the other party a ACK response/C/code. After receiving the ACK information, the two can be connected, and the port is set to the UP state.

Second, one end is set to self -negotiation, and one end is set to compulsory

Send/C/code flow from the negotiation side, the mandatory terminal sends/I/code flow, the forced end cannot provide the confrontation information to the end, nor can it be returned to ACK to respond to the end. However, the compulsory terminal itself can identify/C/code, and believes that the end is a port that matches itself, so set the home port to the UP state directly.

Third, both ends are set to compulsory mode

The two parties send each other/I/code stream. After receiving the/I/code stream one end, they believe that the pair is a port that matches themselves, and the home port is directly set to the UP state.

How does optical fiber work?

The optical fiber is composed of the fine -grained glass wire of the outer plastic protective layer. The glass silk is essentially composed of two parts: a glass material with a low refractive index with a core diameter of 9 to 62.5 μm and a diameter of 125 μm. Although there are some types of fiber different types of optical fibers, the most common types are mentioned here according to the materials used and different sizes. The core layer of the optical fiber is transmitted in the “whole internal reflection” mode, that is, after the optical wiring enters one end of the fiber, reflects back and forth between the core layer and the packet layer interface, and then transmits to the other end of the fiber. The optical fiber with a core diameter of 62.5 μm and the outer diameter of the package layer is 62.5/125 μm.

The difference between multimodal and single -mode fiber?


It can spread hundreds of or thousands of modes, called multi -mode (MM) fiber. According to the radial distribution of the refractive index in the fiber core and the packet layer, it can be divided into level multi -mode fiber and gradient multi -mode fiber. Almost all multi -mode fiber size is 50/125 μm or 62.5/125 μm, and bandwidth (optical information transmission volume) is usually 200MHz to 2GHz. Multi -mode optical terminals can transmit up to 5 kilometers through multi -mode fiber. Taking light emitting diode or laser as a light source.

Single mode:

Fiber that can only spread one mode is called single -mode fiber. Standard single -mode (SM) fiber fiber refractive index distribution is similar to that of step -type fiber, but the diameter of the core of the fiber is much smaller than the multi -mode fiber.

The size of the single-mode fiber is 9-10/125 μm, and the characteristics of unlimited bandwidth and lower loss are more than the multi-mode fiber. The single -mode light end machine is mostly used for long -distance transmission, sometimes it can reach 150 to 200 kilometers. LEDs with a narrow LD or spectrum line are used as light sources.

Difference and connection:

Single -mode device can usually run both on the single -mode fiber or on multi -mode fiber, and the multi -mode device is limited to running on multi -mode fiber.

What is the transmission loss when using optical cable?

This depends on the wavelength of transmission and the type of fiber used.

850nm wavelength when it is used for multi -mode fiber: 3.0 decibel/km

1310nm wavelength when it is used for multi -mode fiber: 1.0 decibel/km

1310nm wavelength when used for single -mode fiber: 0.4 decibel/km

1550nm wavelength when it is used for single -mode fiber: 0.2 decibel/km

What is GBIC?

GBIC is the abbreviation of Giga Bitrate Interface Converter. It is an interface device that converts the Gigabit electrical signal into a light signal. GBIC design can be used for hot insertion. GBIC is an interchangeable product that meets international standards. Due to the flexible exchange of GBIC interface design, the GBIC interface design has a large market quantity in the market.

What is SFP?

SFP is the abbreviation of Small Form Pluggable, which can be simply understood as an upgraded version of GBIC. The size of the SFP module is half lower than the GBIC module, and the number of ports that can be more than doubled on the same panel can be configured on the same panel. The other functions of the SFP module are basically consistent with GBIC. Some switch manufacturers call the SFP module for miniaturization GBIC (Mini-GBIC).

In the future, the light module must support hot insertion, that is, no need to cut off the power, the module can be connected or disconnected with the device. Because the light module is hot -inserted, the network manager can upgrade and expand the system without closing the network. Users will not have any impact. The heat insertion also simplifies the overall maintenance work and enables end users to better manage their receiving modules. At the same time, due to this thermal exchange performance, the module allows network managers to upgrade the transceiver cost, link distance and all network topology according to the network upgrade requirements, and no need to replace the system board.

There are GBIC and SFPs that support this hot -plugging light. Since the appearance size of SFP and SFF, it can be directly inserted on the circuit board. Its future development is worth looking forward to, and may even threaten the SFF market.

What is SFF?

The SFF (Small Form Factor) small sealing light module uses advanced precision optical and circuit integration processes. The size is only half of the ordinary dual -work SC (1×9) fiber transceiver module. Increase the density of the line port and reduce the system cost of each port. And because the SFF small packaging module uses the KT-RJ interface similar to the copper wire network, the size is the same as the common computer network copper line interface, which is conducive to the transition of copper-cable-based network devices to a higher-speed fiber network. In order to meet the sharp growth of network bandwidth demand.

Network connection device interface type

BNC interface

The BNC interface refers to the coaxial cable interface. The BNC interface is used for the connection of 75 Euros coaxial cables. It provides two channels: collection (RX) and hair (TX). It is used for non -balance signals.

Fiber interface

The fiber interface is a physical interface used to connect the fiber cable. There are usually several types of SC, ST, LC, FC. For the 10Base-F connection, the connector is usually a ST type, and the FC is connected to the fiber fiber frame. FC is the abbreviation of FerruleConnector. The external enhancement method is a metal sleeve, and the fastening method is a screw buckle. ST interfaces are usually used for 10base-f, SC interfaces are usually used for 100Base-FX and GBIC, and LC is usually used for SFP.

RJ-45 interface

The RJ-45 interface is the most commonly used interface of Ethernet. The RJ-45 is a commonly used name, which refers to the standardization of IEC (60) 603-7, and uses 8 positions defined by international connection standards (8 stitches). The modular jack or plug.

RS-232 interface

The RS-232-C interface (also known as EIA RS-232-C) is currently the most commonly used serial communication interface. It was formulated by the US Electronics Industry Association (EIA) in conjunction with the Bell System, Modue Small Manufacturer and Computer Terminal Manufacturers in 1970. Its full name is “Data terminal device (DTE) and data communication equipment (DCE) serial binary data exchange interface technical standards”. This standard stipulates that a 25 -foot DB25 connector is used to specify the signal content of each pin of each pin of the connector, and the level of various signals is also specified.

RJ-11 interface

The RJ-11 interface is what we usually call the telephone line interface. RJ-11 is a universal name for connecting accessories developed by Western Electric. Its shape is defined as a 6 -pin connection device. Originally named wexw, X here means “activity”, contacts or threading. For example, we6W has all 6 contacts, numbers from 1 to 6, and the WE4W interface only uses 4 stitches. The two most external contacts (1 and 6) are not used. We2W only uses the middle two stitches (that is, the phone line interface).


With the rapid growth of Internet IP data services, the demand for transmission line bandwidth has continued to increase. Although the DWDM (dense wave division) technology is the most effective method for solving the width expansion of the line, CWDM (thick wave division) technology has advantages in terms of system cost and maintenance.

Both CWDM and DWDM belong to the wave division reuse technology, which can be transmitted together to the single -core optical fiber and transmit it together.

The latest standard of CWDM’s ITU is G.695, which stipulates 18 wavelength channels between 2071nm to 1611nm. Considering the impact of ordinary G.652 optical fiber, 16 channels are generally used. Because the channel interval is large, the components and laser are cheaper than the DWDM device.

The DWDM channel interval is different from the needs of 0.4nm, 0.8nm, 1.6nm, etc., and the interval is small and requires additional wavelength control devices. Therefore, equipment based on DWDM technology is higher than CWDM technology.

The PIN Optical Diode is between P -type and N -type semiconductors with high concentrations of mixed concentrations. A layer of light -doping N -type material is added, called I (Intrinsic, this sign) layer. Due to light doping, the electronic concentration is very low, and a wide depletion layer is formed after diffusion, which can improve its response speed and conversion efficiency.

The APD avalanche Optoelectronics diode, which not only has the effect of light/electricity conversion, but also has an internal amplification effect. Its amplification effect is completed by the avalanche multiplied effect inside the tube. APD is a gain of an increased photovoltaic diode. In the occasion where the sensitivity of the optical receiver is high, the use of APD is conducive to extending the transmission distance of the system.

In order to answer your doubts, the above is what we have organized about Outdoor Industrial D Style Plug 8 Pin Signal Connector Ethernet Rj45 Waterproof Connector, hope it can help you.