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What is the difference between SFP, SFP+ and XFP optical modules?
Knowledge Base + 2024.01.26

I. Recognizing SFP Optical Module

SFP is the abbreviation of SMALL FORM PLUGGABLE, which can be simply understood as the upgraded version of GBIC. the volume of SFP module is reduced by half compared with GBIC module, and it can be configured with more than double the number of ports on the same panel. other functions of SFP module are basically the same as GBIC.

Some switch vendors refer to SFP modules as miniaturized GBICs (MINI-GBICs). The SFP module is half the size of a GBIC module and can be configured with more than double the number of ports on the same panel. the other features of the SFP module are basically the same as those of the GBIC. (Mini-GBIC.) Abbreviation for Gigabit Interface Converter, 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 GBIC interfaces hold a large market share in the market due to their interchangeability and flexibility.


GBIC modules are divided into two main categories:

One is the GBIC module used for ordinary cascading to realize ordinary connection with other switches;

The second is the GBIC module for stacking, which realizes redundant connection with other switches.

SFP modules are more compressed in size and power consumption by placing the CDR and dispersion compensation outside the module.

1. SFP Standardization

SFP transceivers are standardized by a Multilateral Agreement (MSA) between competing vendors.SFPs are designed with the GBIC interface in mind, which allows for greater port density (number of transceivers per inch on the side of the motherboard) than GBICs, hence the term "mini-GBIC". The associated Small Form Factor transceiver (SFF transceiver) is smaller in size than the SFP, but the SFF is soldered to the motherboard as a pin-through-hole device rather than plugged into an edge card slot.

2. SFP Types

SFP transceivers are available in a variety of different transmit and receive types, allowing the user to select the appropriate transceiver for each link to provide the "optical performance" that can be achieved based on the type of fiber available (e.g., multimode or singlemode fiber). Available optical SFP modules generally fall into the following categories: MMF (SX) at 850 nm/550 meters, SMF (LX) at 1310 nm/10 km, XD at 1550 nm/40 km, ZX at 80 km, EX or EZX at 120 km, and DWDM.

SFP transceivers are also available with copper interfaces, enabling host devices designed primarily for fiber optic communications to communicate over UTP network cables. SFPs for wavelength-division multiplexing (CWDM) and single-fiber "bi-directional" (1310/1490 nm wavelength uplink/downlink) are also available.

3. Classification of optical fibers

Optical fiber is divided into two types of multi-mode fiber and single-mode fiber: Among them, multi-mode fiber due to cheaper light-emitting devices as well as construction of simple characteristics, widely used in short-distance communications, multi-mode fiber is divided into 50um core diameter and 62.5um core diameter of two kinds, of which 62.5um is more common, but the performance of the 50um is not as good.

Single-mode fiber is generally used for long-distance communication, core diameter of 9um, single-mode fiber on the transmission distance of 10 kilometers, 20 kilometers, 70 kilometers, 120 kilometers, respectively. General switch manufacturers in the single-mode only provide 10 km and 70 km two models, 20 km products can effectively save the overall cost of the system integrator's specific network program. 120 km products are used for special ultra-long operating environment.

4. Difference of SFP

SFP optical modules usually use dual LC interfaces, in addition to single-core SFP optical modules. From the rate and fiber type can be divided into four kinds of 100 megabit single-multimode and gigabit single-multimode.


Second, the difference between SFP multi-mode and single-mode


Currently in the project encountered a few SFP problems, there are actually or may be related to the type of optical module, so deliberately find some multi-mode and single-mode information.

Here are some concepts and differences between multimode and single-mode SFPs.

According to the wavelength of 850nm/1310nm/1550nm/1490nm/1530nm/1610nm, the wavelength of 850nm is SFP multimode, the transmission distance in the following 2KM;

Wavelength of 1310/1550nm is SFP single-mode, transmission distance in more than 2KM, relatively speaking, the price of these three wavelengths cheaper than the other three.

Bare module if there is no logo is easy to confuse, the general manufacturers will be in the color of the pull ring to distinguish, for example: black pull ring for multi-mode, the wavelength is 850nm, blue, yellow and purple pull ring for single-mode, the wavelength is 1310nm, 1550nm, 1490nm, respectively.


Almost all multimode fibers are 50/125μm or 62.5/125μm in size and have a bandwidth (the amount of information that can be transmitted over the fiber) usually from 200MHz to 2GHz. multimode optical terminals can transmit up to 2km over multimode fibers. Light emitting diodes or lasers are used as the light source. The pull ring or outer body color is black.

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The size of single-mode fiber is 9/125μm, and it has unlimited bandwidth and lower loss than multi-mode fiber. And single mode fiber optic terminals are mostly used for long distance transmission, sometimes up to 100 kilometers. LD or LED with narrower spectral line is used as light source. The pull ring or outside body color is blue, yellow or purple.

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Difference and Connection:

Single-mode fiber is inexpensive, but single-mode equipment is much more expensive than its multimode counterpart. Singlemode equipment typically runs on both singlemode and multimode fiber, while multimode equipment is limited to running on multimode fiber.

With this year's single-mode and multimode SFP modules closer to the current single-mode fiber optic cable and single-mode module adoption has become mainstream. Single-mode is clearly superior to multimode types in use.


The difference between SFP, SFP + and XFP


Many people are not clear about the difference between SFP+ and SFP, XFP, so sometimes bring unnecessary trouble (security weak circle). 10G module has experienced the development from 300Pin, XENPAK, X2, XFP, and ultimately achieve the same size as the SFP to transmit 10G signals, which is the SFP +. SFP + by virtue of its miniaturization and low-cost advantages to meet the device SFP+, with its advantages of miniaturization and low cost, meets the demand for high-density optical modules, and has gradually replaced XFP as the mainstream of the 10G market.

        SFP package --- hot-swappable small package module, the current maximum rate of up to 4G, mostly using LC interfaces.

        SFP+ package --- standard package, the operating rate is 10G, can meet the Ethernet 10G applications.

        XFP package - a standardized package for serial 10G optical transceiver module.


SFP+ optical module advantages:

1, SFP+ has a more compact form factor than X2 and XFP packages (same size as SFP);

2, can be directly connected with the same type of XFP,X2,XENPAK;

3, the cost is lower than XFP,X2,XENPAK products.


The difference between SFP and SFP+:

1, SFP and SFP + appearance of the same size;

2, SFP's maximum rate up to 4G, SFP + rate is 10G;

3, SFP protocol specification: IEEE802.3, SFF-8472;

4, SFP + support digital diagnostics.


The difference between SFP+ and XFP:

1, SFP + and XFP are 10G fiber optic modules, and with other types of 10G modules can be interoperable;

2, SFP + than XFP smaller size;

3, because of the smaller size, SFP + signal modulation functions, serial / deserializer, MAC, clock and data recovery (CDR), as well as electronic dispersion compensation (EDC) functions from the module to the motherboard card;

4. XFP-compliant protocol: XFP MSA protocol;

5, SFP + compliance protocol: IEEE 802.3ae, SFF-8431, SFF-8432;

6, SFP + is more mainstream design;

7, SFP + protocol specification: IEEE 802.3ae, SFF-8431, SFF-8432.


Aging test of SFP module


Quality is important for all products.

In order to control the quality of products, we will do some tests, including incoming inspection, product parameter test, distance test, switch test and aging test.

A. Purpose of aging test:

1.To find out the faulty products in advance before shipment

2. Prohibit faulty products from leaving the factory

3. Reduce the scrap rate

4. Ensure the stability of the product after shipment.


B. Aging test process:

1. Install the module to the aging board

2. Turn on the power

3. Connect the male and female plugs

4. Start the aging machine switch

5. Close the aging chassis door

6. Click on the display of the run

7. Temperature set value is 75, humidity set value is 0.

8. Aging time is about 24 hours

9. Aging is complete, put it away

10.Test transmission and reception