What is SFP Module? An Ultimate Guide

You probably know the SFP module if you know the Ethernet switch. In fact, we can see it almost everywhere in modern fiber optic networks. But what is it exactly?

This post is a complete guide to this product. It will cover its definition, working Principle, classified types, and applications.

Now let’s go on.

Table of Contents

• What is an SFP module?

• Why is it important? 

• How many types are there? 

• How to choose the suitable SFP module?

• FAQ

What is an SFP module?

An SFP module is a small form factor pluggable optical transceiver that fits into the SFP port of the networking switch or other device. Sometimes, It is also known as the mini-GBIC (gigabit interface converter) or SFP transceiver. 

A typical SFP fiber module consists of a cage, PCBA, chip, and TOSA+ROSA (sometimes maybe BOSA for BiDi transceiver). See the below photo.

Although it appeared later than the GBIC and SFF form factor, SFP shares an excellent ratio on the market and still growing now. Furthermore, it replaces those two types rapidly. We believe the most critical influence factors are: 

• Hot Pluggable: Plug in and Plug out without restarting the switch

• Compact Size: High port density for more bandwidth

• Smart real-time monitor: enhanced DDM (DOM) function makes simple operation

To help understand the basics, we briefly introduce the SFP MSA. It stands for small form factor multi-source agreement – the critical MSA for the SFP module, including INF-8074i, SFF-8431, and SFF-8472. And this agreement defines the mechanical dimensions, electronic/optical interface, and Diagnostic Monitoring Interface.

Why is the SFP module important? 

Imagine your switch without an optical module. How can you achieve high speed? The answer may be through copper cable. However, it is not viable because of thickness, cost, and short-distance limitations.

That is where the SFP module plays. By inserting a transceiver into the switch port, you could bridge communicate with another switch for tens to hundreds of kilometers. 

For example, with a 1G SFP SX, the max distance reaches 550m over multimode OM2 fiber. While with a 1G SFP LX module, the max span can be 20km at single mode fiber. 

How many types of SFP modules are there?

Since so many SFP modules are on the market, many people usually need to know the different classifications. Therefore, choosing the correct transceiver becomes a challenge.

Next, we will try to categorize them based on various standards.

By SFP Transceiver Speed

• 100BASE SFP: Usually stands for 100Mbps and 155Mbps speed, widely used in fast Ethernet, SDH/SONET &ATM. Most of the devices have been upgraded to 1G or higher speed.

• 622M SFP: Special for SDH/SONET equipment. Few manufacturers provide this type.

• 1000BASE SFP: Also known as 1G or Gigabit, it is the most popular transceiver in the datacom communication and with the most supplier choices.

• 2G SFP: Including 2G fiber channel and 2.5G speed, suitable for 2x FC SAN switch and SDH/SONET device.

• 3G SFP: Including 2.97G and 3.07G speed, suitable for video transmission,  CPRI (Common Public Radio Interface), OBSAI (Open Base Station Architecture Initiative)

• 4G SFP: Specific speed of 4.25G, suitable for 4x FC SAN switch

• 8G SFP: Specific speed of 8.5G, suitable for 8x FC SAN switch

By SFP Media Type

• Copper: Transmit the signal with traditional copper cables, such as network cable or DAC cable

• Multimode Fiber (MMF): Supports OM1, OM2, OM3, OM4, and OM5 cabling. Higher fiber grade provides better performance.

• Singlemode Fiber (SMF): Suitable for 9/125 single mode fiber cabling, provides the max link distance.

By SFP Transceiver Distance

• T: Including 100BASE-T, 1000BASE-T, 2.5GBASE-T, 5GBASE-T, Typcial distance 100m over Cat5 cable.

• SX: Stands for short reach. It is defined in the IEEE 802.3z; 1000base-SX reaches 550m on multimode fiber.

• LX: Stands for extended reach. It is defined in the IEEE 802.3z, 1000BASE-LX reaches 10km on single mode fiber.

• EX: Stands for extended reach. It is defined in IEEE 802.3z. 1000BASE-EX reaches 40km on single mode fiber.

• ZX: Also Stands for extended reach. It is defined in IEEE 802.3z, 1000BASE-ZX reaches 70km (or 80km) on single mode fiber.

By Application

• Regular SFP: Most commonly transceiver with a duplex fiber

• CWDM SFP: Support CWDM transmission to improve the bandwidth in one fiber

• DWDM SFP: Support DWDM  transmission to maximize the bandwidth while saving the fiber cabling

• BiDi SFP: Bi-directional transceiver for transmit and receiver in simplex fiber                

• SDH/SONET SFP: mainly speed including 155Mbps, 622Mbps, and 2.5Gbps, suitable for SDH/SONET platform

• Fiber Channel SFP: Covers the speed of 1G, 2G, 4G, and 8G, mainly used in the storage network

• Video SFP: Support HD-SDI/3G-SDI/6G-SDI/12G-SDI, focus on the video transmission market

• PON SFP:  Include the GPON and EPON, standards for Passive optical networking, mainly for the FTTX application

• SFP Cable: It is a direct attached cable with an SFP connector on two ends, a lower-cost solution for very short length

• 

• Figure 2: LC duplex vs. SC simplex vs. RJ45 SFP module (From left to right)

By Connector Type

• LC SFP: LC is the default connector for most SFP transceivers

• SC SFP: Some BiDi transceivers Assemble SC connectors but share a very small shipment

• RJ45 SFP: This transceiver has a female RJ45 connector to allow network cable insert.

By Operating Temperature

• Commercial grade: It’s the typical transceiver that supports 0~70C temperature. Usually, with the best pricing and cost ratio, and suitable for a standard indoor environment like a data center or enterprise.

• Industrial grade: It’s a hardened transceiver that supports -40~85C temperature. Suitable for industrial switches in the outdoor environment. But they are offered at a much higher price.

• Extended grade: This one is not the standard type. It can handle the -10~85C temperature.

In fact, there are many other ways to categorize them. However, the most common methods are classified by data speed and application. 

Significantly, the same transceiver maybe with various types in different classified ways. For example, the compatible Cisco GLC-TE will be categorized in multiple charts, including 1G, Copper, T, RJ45, and industrial transceiver. 

How to choose the suitable SFP Module for your networking? 

We help more than 1400 clients choose the suitable transceiver quickly. Here are the essential tips.

1. Check your switch (or other network devices) port-supported speed and then match the correct SFP.

2. Know your existing network cabling types. If you have a multimode fiber cabling structure, then choose the multimode SFP. If you have a single mode fiber cabling, a single mode transceiver is the only choice.

3. Know your target link distance and link budget. But remember, choose an SFP supporting longer transmission distances than expected. Otherwise, poor fiber optic cable or a dirty fiber end-face may cause a failed link.

4. Considering the operating temperature. For a typical indoor environment, using a commercial-grade transceiver is enough. While in harsh outdoor applications, you should use the industrial transceiver.

5. Remember to check compatibility with the supplier before ordering. Because the switch can not recognize an incompatible transceiver, that will waste your money and valuable time. So always choose a proven compatible transceiver.