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Network Attached Devices Interface Type Wiki
Knowledge Base + 2024.02.19

There are four optical modules commonly used in Ethernet switches, namely, SFP (Small Form-factor Pluggabletransceiver) Small Form-factor Pluggable Transceiver, GBIC (GigaBit Interface Converter) Gigabit Ethernet Interface Converter, XFP (10-Gigabit) Small Form-factor Pluggable Transceiver, and XENPAK (10 Gigabit EtherNet TransceiverPAcKage) 10-Gigabit Ethernet Interface Transceiver Aggregate Package. Small Form-factor Pluggabletransceiver, GBIC (GigaBit Interface Converter) Gigabit Ethernet Interface Converter, XFP (10-Gigabit Small Form-factor Pluggable Transceiver) 10-Gigabit Ethernet Interface, and XENPAK (10 Gigabit EtherNet TransceiverPAcKage) 10-Gigabit Ethernet Interface Transceiver Collection Package.

01、Fiber Optic Connector

Fiber optic connectors consist of an optical fiber and a plug at each end of the fiber, which consists of pins and a peripheral locking structure. According to different locking mechanisms, fiber optic connectors can be divided into FC type, SC type, LC type, ST type and KTRJ type.

Fiber Optic Connector.png

FC connector adopts a thread locking mechanism, which is a kind of fiber optic movable connector invented earlier and used most.

SC is a rectangular connector, developed by NTT, does not use threaded connection, can be directly plugged and unplugged, and compared with FC connector has a small operating space, easy to use. It is very common for low-end Ethernet products.

LC is a Mini type SC connector developed by LUCENT, with smaller size, has been widely used in the system, is a future direction of fiber optic movable connector development. Low-end Ethernet products are very common.

ST connector is developed by AT&T, with bayonet locking mechanism, the main parameters and indicators of FC and SC connectors are comparable, but in the company's application is not common, usually used in multi-mode device connection, and other manufacturers of equipment docking used more.

KTRJ pin is plastic, through the steel pin positioning, with the increase in the number of insertion and extraction, the mating surface will be worn, long-term stability is not as good as ceramic pin connector.

The transmission loss when using fiber optic cables depends on the wavelength of the transmitted light and the type of fiber used.

850nm wavelength for multimode fiber: 3.0dB/km

1310nm wavelength for multimode fiber: 1.0 dB/km 1310nm wavelength for single-mode fiber: 0.4 dB/km 1550nm wavelength for single-mode fiber: 0.2 dB/km


GBIC stands for Giga Bitrate Interface Converter and is an interface device that converts gigabit electrical signals to optical signals.GBIC is designed to be hot-swappable.GBIC is an interchangeable product that conforms to international standards. Gigabit switches designed with the GBIC interface hold a large share of the market due to their interchangeability.


03 SFP

SFP stands for SMALL FORM PLUGGABLE and can be simply understood as an upgraded version of GBIC. the SFP module is half the size of the GBIC module and can be configured with more than double the number of ports on the same panel.


The other functions of SFP module are basically the same as GBIC. Some switch vendors call SFP modules miniaturized GBICs (MINI-GBICs).

Future optical modules must support hot-plugging, that is, without cutting off the power supply, the module that can be connected or disconnected from the device, because the optical module is hot-pluggable, network managers do not need to shut down the network to upgrade and expand the system, the online users will not cause any impact.

Hot-swappability also simplifies total maintenance and enables end users to better manage their transceiver modules.

At the same time, because of this hot-swap performance, the module allows network managers to upgrade their network requirements, transceiver costs, link distances, and all the network topology of the overall planning, without the need to replace all the system boards.

Support for this hot-swap optical module currently GBIC and SFP, due to the SFP and SFF appearance is about the same size, it can be directly inserted into the circuit board, in the package to save space and time, and the application is quite wide, therefore, its future development is worth looking forward to, and may even threaten the SFF market.

04 SFF

SFF (Small Form Factor) small encapsulated optical modules using advanced precision optics and circuit integration process, the size of the ordinary duplex SC (1X9) type fiber optic transceiver module half of the same space can double the number of optical ports, you can increase the density of line ports, reduce the cost of the system per port.


And because the SFF small package module with a copper network similar to the KT-RJ interface, the size of a common computer network with the same copper interface, is conducive to the transition of the existing copper-based network equipment to a higher speed fiber optic network to meet the network bandwidth needs of the rapid growth.

Network Connection Device Interface Type

01 BNC interface

BNC interface refers to the coaxial cable interface, BNC interface is used for 75 ohm coaxial cable connection, providing receive (RX), send (TX) two channels, it is used for unbalanced signal connection.

BNC interface.jpg

02 Fiber Optic Interface

Fiber optic interface is a physical interface used to connect fiber optic cables. Usually there are several types such as SC, ST, LC, FC and so on. For 10Base-F connection, the connector is usually ST type, and the other end of FC is connected to the fiber optic step frame.

Fiber Optic Interface.png

FC is the abbreviation of FerruleConnector, its external reinforcement is the use of metal bushings, fastening method for the screw buckle.ST interface is usually used for 10Base-F, SC interface is usually used for 100Base-FX and GBIC, LC is usually used for SFP .

03 RJ-45 Interface

The RJ-45 interface is the most commonly used interface for Ethernet. RJ-45 is a common name for a modular 8-position (8-pin) jack or plug standardized by IEC (60) 603-7 and defined by the international connector standard.

RJ-45 Interface.png

04 RS-232 Interface

The RS-232-C interface (also known as EIA RS-232-C) is the most commonly used serial communications interface.

RS-232 Interface.jpg

It was developed in 1970 by the Electronic Industries Association of America (EIA) in conjunction with the Bell System, modem manufacturers, and computer terminal manufacturers as a standard for serial communications. Its full name is "data terminal equipment (DTE) and data communications equipment (DCE) between the serial binary data exchange interface technology standards.

The standard specifies the use of a 25-pin DB25 connector, the signal content of each pin of the connector is specified, and the levels of various signals are also specified.

05 RJ-11 interface

The RJ-11 interface is what we usually call the telephone line interface.

RJ-11 interface.png

RJ-11 is the generic name used for the connector developed by Western Electric. The form factor is defined as a 6-pin connector.

The original name was WExW, where the x stands for "active", contact or wire tie.

For example, WE6W has all 6 contacts numbered from 1 to 6, WE4W interface uses only 4 pins and the two outermost contacts (1 and 6) are not used, and WE2W uses only the middle two pins (i.e. for telephone line interface).


06 AUI Interface

AUI interface is specially used for connecting thick coaxial cables. Early NICs had such an interface to connect with hubs and switches to form a network, but now it is generally not used.

AUI Interface.jpg

AUI interface is a "D" type 15-pin interface, previously used in the token ring network or bus type network, you can use the external transceiver transceiver (AUI-to-RJ-45), to realize the connection with the 10Base-T Ethernet network.

07 FDDI Interface

FDDI is one of the mature LAN technologies with the highest transmission rate, has the characteristics of the timing token protocol, supports a variety of topologies, and the transmission media is optical fiber.

FDDI Interface.png

Fiber Distributed Data Interface (FDDI) is a set of protocols for sending digital signals over fiber optic cables developed by the American National Standards Organization (ANSI).FDDI uses a dual-ring token, and the transmission rate can be up to 100 Mbps.


CCDI is a variant of FDDI that uses twisted-pair copper cable as the transmission medium, and data rates are typically 100 Mbps.

FDDI-2 is an extended protocol of FDDI that supports voice, video and data transmission, and is another variant of FDDI called FDDI Full Duplex Technology (FFDT), which utilizes the same network structure as FDDI, but the transmission rate can be up to 200Mbps.

Since the use of optical fiber as a transmission media has many advantages such as large capacity, long transmission distance, and strong anti-jamming ability, it is commonly used in metropolitan area networks (MANs), backbone networks in campus environments, and environments where networks are distributed in multiple buildings.

08 Console Interface

This interface is used to configure the switch, so only managed switches have it.

Also note that not all managed switches have it, that is because there are various ways to configure the switch, such as through Telnet command line, Web, TFTP, etc.

Console Interface.jpg

But note that the Console port used for switch configuration is not the same for all switches, some use the same RJ-45 type Console interface as Cisco routers, as shown in the figure.