SFP Module: What’s It and How to Choose It?

SFP module is a compact, hot-pluggable optical transceiver module widely used for telecommunication and data communications applications.

It is also known as a small form-factor pluggable or mini GBIC. The SFP transceiver module is not standardized by any official standards body but rather by a multi-source agreement (MSA).

Optical transceiver is widely used to connect network devices,
such as switches, NIC (network interface card), and media converters.
It makes SFP module necessary in fiber optical connections.
SFP module has been an industry workhorse for over 20 years.
This post is going to explore those problems: SFP module types and applications and how to choose suitable SFP modules are included.

What Is SFP Module?

SFP module is a compact, hot-pluggable optical transceiver module, which is widely used for both telecommunication and data communications applications.
It is also known as small form-factor pluggable or mini GBIC (gigabit interface converter).
Its SFP port accepts both optical modules and copper cables. That’s why it’s developed and supported by many network component vendors.
The SFP transceiver module is not standardized by any official standards body, but rather is specified by a multi-source agreement (MSA).
SFP module also supports SONET, Gigabit Ethernet, Fibre Channel, and other communication standards.
In addition, SFP has replaced GBIC in most applications because of its small size.

How Many Types of SFP Module?

SFP transceiver module comes in various types based on different classification standards.
As the cable types are different, we can divide SFP modules into single-mode and multimode.
The transmission rate of SFP module is available from 100Mbps up to 4Gbps or more, and the working distance can range from 500 meters to 100 kilometers.

In addition, CWDM SFP modules and DWDM SFP modules are also available for WDM links. Copper SFP modules allow communications over twisted-pair networking cables.

SFP modules also come with different features, such as DDM (Digital Diagnostics Monitoring), DOM (Digital Optical Monitoring), and RGD (rugged) grade transceivers.

DDM and DOM allow users to check the SFP module’s real-time parameters, such as input power, output power, and temperature, while RGD is well-suited for industrial networking applications, such as manufacturing automation, substation, and smart transport systems.

Classification Table

For more detailed information about SFP transceiver module, you could read: How Many Types of SFP Transceivers Do You Know

Usually, SFP ports use in Ethernet switches, routers, firewalls and NIC cards.
SFP modules connect devices to fiber or copper cables like Cat5e. Other types of SFP optical transceivers like 3G video SFP and 12G video SFP.
They are also used in HD cameras or monitoring systems.

More information about HD video transceiver has illustrated in this post: Understanding Video SFP Transceivers

Common Questions About SFP Module

1. DDM, DOM, RGD-What functons do they represent?

DDM, DOM and RGD are common in SFP transceiver names, which makes users confused.

DDM (Digital Diagnostics Monitoring) lets users check SFP modules’ real-time parameters.

Such as input power, output power and temperature.

DOM (digital optical monitoring) is like DDM, allowing users to check parameters of the SFP.

RGD means the SFP is a “rugged” grade transceiver

It is well fit for industrial networking applications such as

● manufacturing automation,

● substation

● smart transport systems.

2. What’s the difference between singlemode SFP and multimode SFP?

There are three main differences between Singlemode SFP (SMF SFP) and multimode SFP (MMF SFP)

① Fiber： Singlemode fiber has a smaller core than multimode fiber, and it allows unlimited bandwidth and lower loss. While multimode fiber can propagate multiple modes of light.

② Transmission distance. Singlemode SFP transceiver is often used in long-run links up to 120km. Multimode SFP module is used in short applications.

③ Cost. Singlemode SFP is more expensive than multimode SFP due to the use of different light-emitting units.

3. What’s the difference between SFP and SFP+?

SFP and SFP+ have the same size and appearance.
The main difference between SFP and SFP+ is that SFP is often used for 100Base or 1000Base applications, while SFP+ is used in Gigabit Ethernet applications.
The data rate and transmission distance of them are also different.
For example, SFP supports speeds up to 4Gbps Fibre Channel transceiver, while the speed of SFP+ transceiver is up to 10.3125Gbps.

4. Can we use SFP hardware in SFP+ slots?

In many cases, SFP+ ports accept SFP optics, but the speed will be down to 1G instead of 10G.
However, SFP+ optics can not plug into the SFP port, because SFP+ does not support speed under 1G.
In addition, almost all SFP+ ports on Cisco switches can support SFPs, but many SFP+ ports of Brocade switch only support SFP+ optics.

5. How to maintain SFP module?

There are several aspects to maintaining SFP transceivers.

• Optical port protection.
• Keep the end face clean; avoid prolonged exposure to the SFP port in the air.
• Avoid scratching the end face or sleeve, etc.
• Use the SFP module correctly.
• Keep the optical transceiver work at the normal level
• Plug and insert the SFP transceiver gently to reduce accidental damage.
• Keep the using environmental humidity of the SFP transceiver normal.

What to Consider When Choosing SFP Module?

When selecting SFP modules, compatibility is often the most important factor to consider. It is essential to ensure that the SFP module is compatible with our devices. Users should also consider the transmission rate, distance, and cost when selecting SFP modules.

When it comes to buying SFP modules, Cisco SFP modules are the preference for many users.
However, with the prosperity of the optical transceiver market, things are changed
Multitudes of third-party optical transceiver vendors begin to offer cheaper SFP modules that have the same performance as Cisco SFP.
Then what to consider when selecting SFP modules?

SFP Module Compatibility

When purchasing third-party SFP optical transceivers, compatibility is often the most parameter users care about.
Before placing your order, you can check the vendors’ optics testing center to confirm whether the SFP module is compatible with your devices.
Or just ask the sales rep for details about the SFP transceiver compatibility.

New SFP Module and Second-Hand SFP

There are both new and second-hand SFP transceivers in the market.
Learning to discriminate against them can avoid unnecessary loss.
Usually, the used SFP module may have scratches in its appearance and optical port.
Besides, testing the optical power, and comparing the test result with the specifications is another effective way.
If the result is much different, be careful, it may be a second-hand SFP module.

SFP Module Price

Compared with Cisco SFP or other brand SFP modules, third-party SFP optical transceivers are more cost-effective.
Under normal conditions, except for the price, there is no difference between the performance of compatible 1G SFP and OEM SFP modules.
That’s why compatible SFP modules are popular in the market.
Users can choose the right compatible SFP optical transceivers from reliable vendors according to their needs at a cheap price.

Temperature Stability

We mainly use SFP transceiver module in data centers or on switches where the temperature may be different in a large range.
Too high or too low temperatures can affect the optical power and optical sensibility.
Therefore, temperature stability is an important factor to ensure SFP module work normally.

SFP Module Quality and After-Sale Service

Nobody can ensure the SFP modules received are 100% normal. And the service life of optical transceiver is generally 5 years among many vendors. It’s difficult to tell the quality is good or bad in the first year. Therefore, choose a reliable SFP vendor is important.