What is an Optical Transceiver?

Definition

Optical transceiver, also known as fiber optic transciever, is a device that uses fiber optic technology rather than conventional electrical wire to send and receive data. It is made of optoelectronic devices, functional circuits and optical interfaces. Optoelectronic devices include two parts: transmitter and receiver. To put it simple, a fiber optic transceiver serves as a photoelectric converter. The transmitter converts an electrical signal into a light signal, and then the receiver converts the light signal into an electrical signal after transmission through the optical fiber. Fiber optics is a rapidly growing field and can communicate complex information faster than conventional methods of transferring data.

optical module

How Does It Work?

The optical transceiver module is composed of both a transmitter and a receiver that are arranged in parallel so that they can operate independently. In the fiber optics, the transmission of data is in the form of light, because the transceiver has electronic components to encode or decode data into light pulses and then sends them to the other end as electrical signals in order to be utilized by an electronic device. The transmitter converts an electrical signal into an optical signal, which is connected with a connector and transmitted through a fiber optic cable. The light entering from the end of the cable is connected to a receiver where a semiconductor detector converts the light back into an electrical signal.

transmitter-and-receiver

Package

According to the package, there are six common types of fiber optic transceivers popular in the market, namely GBIC, XFP, SFP, SFP+, XENPAK, and X2.

1. GBIC (Gigabit Interface Converter). GBIC is designed for hot-plug. It is an interchangeable product meeting international standards. GBIC optical modules are used widely before SFP package.

2. SFP (Small Form-factor Pluggable). SFP is an upgraded version of the early GBIC module. It features smaller volume and higher integration than GBIC fiber module. It is currently the most popular optical module in the market.

3. SFP+. SFP+ optical module has been upgraded based on SFP with a higher transmission rate, usually up to 8.5G or 10G.

4. XFP. XFP transceiver (10 Gigabit Small Form Factor Pluggable) is a hot-swappable, independent of the communication protocol optical transceiver. XFP is usually used for 10Gbps SONET/SDH, Fibre Channel, Gigabit Ethernet and other applications, but also for CWDM DWDM link.

5. XENPAK. XENPAK is a multisource agreement (MSA), instigated by Agilent Technologies and Agere Systems. It’s a 10 Gigabit Ethernet optical transceiver which is independent of transceiver circuits and optical components. It can be plugged into a router or switch. But now XENPAK has been replaced by more compact devices providing the same functionality.

6. X2. X2 transceiver is a 10Gbps modular fiber optic interface intended for use in routers, switches and optical transport platforms. X2 modules are smaller and consume less power than XENPAK modules, but larger and consume more energy than XFP and SFP+ transceivers.

differen types of transceivers

Optical Transceivers are Used in a Variety of Applications

One of the most important attributes of optical transceivers is their ability to be compatible in a variety of communication applications. Most manufacturers choose them because they fit in a small footprint, and they are reliable. Besides, compatibility is one of the most common considerations in fiber optic transceivers. Take SFP fiber optic transceiver as an example, a SFP fiber optic transceiver on a network device (such as a switch, router, media converter, or similar devices) provides the device with a modular interface so that the user can easily adapt to various fiber optic or copper networking standards. They are designed to support SONET (Synchronous Optical Networking), Gigabit Ethernet, Fibre Channel, and other communications standards.

Conclusion

This article briefly tells about what an optical transceiver is, comprising its definition, its working mode, different types according to package and its usage. I hope it may be helpful to you!

SFP28 and QSFP28 Transceivers Cabling Solutions

Due to the increasing number of connected devices in use and their need for fast cloud-based data processing, the Ethernet interconnect standard widely used in data centers is evolving to move data more quickly and efficiently, which has driven the development of a 25Gbps version of Ethernet. Before 25G Ethernet was proposed, the next speed upgrade for data centers was expected to be 40G Ethernet (using four lanes of 10G) with a path to 100G defined as using 10 lanes of 10G as shown in the following table. However, the 25G Ethernet standard can provide a path to 100G and achieve higher total bandwidth than 40G. This article will discuss the different connection methods between 25G SFP28 and 100G QSFP28 transceivers.

total bandwidth of differnet Ethernet network

Note: 100G QSFP28 can be interfaced with 12-fiber MTP connector or duplex LC connector. In this post, the QSFP28 modules we mentioned all have MTP interface.

Direct Connectivity Solution

According to standard, since QSFP28 is 100G interface, SFP28 is 25G interface, four SFP28 transceivers must be needed to connect to one QSFP28 transceiver to achieve 25G to 100G transmission. In this scenario, an 8-fiber MTP-LC harness will be required to direct connect a QSFP28 port to the four corresponding SFP28 ports. This harness cable has four duplex LC connectors and the fibers will be paired in a specific way, assuring the proper polarity is maintained. Keep in mind that this direct connectivity method only recommended for short distance within a give row or in the same rack or cabinet.

Direct Connectivity Solution

Interconnect Solutions

Solution 1: This interconnect solution shown in the image below allows for patching on both ends of the optical network. The patching on the QSFP28 end is accomplished by using Type-A non-pinned MTP to non-pinned MTP jumper, which connects to the trunk cable, while the patching on the SFP28 end is accomplished using MTP modular cassette and duplex LC patch cable.

interconnect solution 1

Solution 2: In this scenario, a Type-B non-pinned MTP to duplex LC breakout cassette will be used to breakout an 8-fiber QSFP28 transceiver into a 2-fiber SFP28 patching field. This solution does reduce the amount of system attenuation by removing a MTP connector pair, however, it would be that the port breakout module has a limited tail length. Besides, this cabling solution only works best when the active equipment being connected is within the same row.

interconnect solution 2

Solution 3: This interconnect solution allows for an easy upgrade path moving from 2-fiber to 8-fiber connectivity. To connect to the SFP28s ports use the 8-fiber harness as shown in the following diagram, and an 12-fiber MTP trunk cable would be used from the adapter panel for the QSFP28 connectivity, thus allowing a mix and match upgrade patch without having to change out the patch panels. The SFP28 transceiver ports need to be located in the same chassis, which creates less flexibility.

interconnect solution 3

All the products introduced in the above solutions including SFP28 transceivers, QSFP28 transceivers, MTP breakout cassette, MTP adapter panel, MTP trunk cable, etc. can be purchased in FS.COM. We provide free and the same day shipping to the US now.