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SFP Optics transceiver Buying Guide

SFPs are used to plug in network devices and connect to network cables. With the diversification of applications, SFP transceiver modules are also diverse. So, how to choose the SFP module that best suits your needs? Do you want to upgrade your fiber switches and buy the right SFP optics for your network, but don't know where to start or how to choose the right SFP optics? Are you confused about the new SFP optics terms and parameters? This blog post will provide you with some practical advice designed to help you choose a compatible optical module with high compatibility and low cost.

What is the SFP?

SFP, also known as small form-factor pluggable, is a modular hot-swappable transceiver interface for Ethernet media converters and switches.
Replace older GBIC modules previously used (sometimes still called mini GBX)
Helps send ethernet data over optical fiber cable (or copper versions with standard RJ, 45 connectors)
The advantage of using SFPs compared to fixed interfaces (e.g. modular connectors in Ethernet switches) is that individual ports can be equipped with any suitable type of transceiver as needed.
When trying to transmit over optical cable, these are your laser transmitter and receiver, and they easily plug into your media converter or switch with no additional configuration. It's a very simple concept, but there are a lot of factors to take into account when selecting the proper SFP for your application.

SFP Applications:

Fiber optic connections between all devices on an IP Network
Used in Managed Switches, Media Converters, and Self-Managed Switches
Often the highest level of flexibility for fiber type, connector use, and distance

Factors for choosing an SFP transceiver

Before diving into the details of SFP optics, there are some key things you must consider when purchasing a new SFP optics. First, consider your switch data rate, fiber type, wavelength, transmission distance, compatibility, project budget, and more. After sorting out these details, you should have narrowed down your SFP optics choices.

Form Factor

The small form-factor pluggable transceivers have derivated into multiple form factors. Hot SFP types are 1G SFP, 10G SFP+, 25G SFP28, 40G QSFP+, 100G QSFP28. SFP transceivers with different form factors support corresponding speed. Check the equipment port types, choose a matching form factor.

SFP Fiber Type

Another factor to consider when choosing SFP optics is the type of fiber in the existing cabling network or the type of fiber planned for new deployments. Different types of optical cables directly affect the transmission rate and distance of the network. Standard fiber optic cables are divided into multimode fibers and single mode fibers.
Multimode fiber can carry many rays (modes) at the same time because the cores have different optical properties; in fact, light traveling the shortest path (down the middle) travels the slowest. Due to the limited range due to dispersion, it is often used as a wire for sites less than one kilometer in length. It is available in two core sizes: 62.5 μm and 50 μm.
A single-mode fiber cable has a smaller core size of 9 microns and a single optical route capable of transmitting data over more considerable distances of up to 180 kilometers. It necessitates more expensive equipment, runs in the 1310 and 1550 nm wavelength ranges, and is generally used for long-distance LAN, cable TV, and telephone applications.

SFP Wavelength

The third aspect to consider is wavelength. Matching should be considered in combination with the wavelength and fiber type of the opposite SFP transceiver.
Light is defined by its wavelength. It is a member of the spectrum, and each frequency (sometimes called a color) of light has a wavelength associated with it. Wavelength and frequency are related. Generally, shorter wavelength radiation is determined by its wavelength, while longer wavelength radiation is determined by its frequency.
The three central wavelengths for fiber transmission are 850, 1310, and 1550 nm. These wavelengths are used in fiber because they have the lowest attenuation on the fiber. There is a direct relationship between wavelength and its rate of attenuation; the longer the wave, the lower the attenuation. For SFP, 850nm is suitable for short-distance transmission, and the cost is lower; 1310nm is suitable for medium and long-distance transmission, but the cost is high; 1550nm is generally used for long-distance transmission with the highest price.

SFP Transmission Distance

Estimate how far between the two ends. If the transmission medium is optical fibers, choose multimode SFP transceivers for short-reach applications and single-mode SFPs for long-distance transmission. For the former, MMF SFPs are frequently used within a kilometer, such as 30m, 100m, 300m, 400m, 550m. 2km is also available in the market. For the latter, a regular SMF SFP can reach up to 10km. Besides, you can choose from 20km, 40km, 80km, 100km, 120km for ultra long haul networks.
 
For instance, QSFPTEK offers multimode 100GBASE-SR4 QSFP28 that can reach over OM4 fibers and single-mode 100G QSFP28 with a selection of 2km-IR4, 10km-LR4/4WDM-10/PSM4, 40km-ER4, and 80km-ZR4. If the transmission medium is copper cable, do not expect long-distance transmission. The maximum transmission distance of electrical port modules on the market can generally reach 100m.

SFP Data Rate

Your SFP transceiver with fiber or copper wires is for connecting two networking devices such as Ethernet switches. Hence figuring out the device port data rate is the key to SFP transceiver data rate selection. The typical port speed of Ethernet switches is 155Mbps, 1Gbps, 10Gbps, 25Gbps, 40Gbps, 100Gbps, and 400Gbps.

Connector Type

For businesses that need to reutilize existing cabling, what is the type of your fiber optic cable connector? Choose a corresponding SFP connector type to match with the fiber cables.Therefore you also need to consider the connector types related to SFP transceivers, for example LC, SC, and MTP/MPO are three fiber SFP transceiver connector types.
LC and MTP/MPO connectors are available for 40G QSFP+ and 100G QSFP28. LC and SC connectors are found on 1G SFPs.
The following table is about connector types related to SFP transceivers:
 
Module Type Connector Type
SFP RJ45, LC, SC
SFP+ RJ45, LC
QSFP+ LC, MTP/MPO
QSFP28 LC, MTP/MPO

Working Temperature and Compatibility

Three levels of SFP transceivers are: commercial temperature range (COM: 0~70°C), extended temperature range (EXT: -20°C~85°C), and industrial temperature range (IND: -40°C~85°C). In general, transceiver vendors will supply commercial SFPs and industrial SFPs for the same model. IND modules have a higher level of extreme temperature resistance.
SFP compatibility is due to the inserting equipment brand and models. Be mind buying an SFP that is fully compatible with equipment. Heyoptics provides multiple brands compatible transceiver modules, some of the main-stream brands are:

SFP DDM/DOM

DDM is capable of providing component monitoring on transceiver applications in great detail.
The interface itself is capable of generating alarms and warning flags which alert the host system when operating parameters fall outside of a set of ‘normal operating’ rules. This allows the end user to isolate faults and predict failure.
DOM gives you the ability to monitor the transmit and receive power of the optical transceiver module, its temperature and supply voltage. Each system can be configured to monitor transceivers that are in operation either globally or by specific port.
With DOM console message and Syslog messages are sent if operation falls below or rises above the specific transceivers manufacturer thresholds. Most modern transceivers support DOM functions.
If you want to learn more about DDM/DOM, please refer to the blog: DDM/DOM of SFP Transceiver

Common SFP Optics Terms

CWDM SFP

CWDM SFP is a kind of optical transceiver which combines the CWDM technology. Similar with the traditional SFPs, CWDM SFP is also a hot-swappable input/output device that plugs into an SFP port or slot of a switch or router, and links the port with the fiber-optic network. It is convenient and cost-effective to use Gigabit Ethernet and Fibre Channel (FC) in campuses, data centers, and metro access networks. The CWDM SFP enables the transmission of up to 18 channels on a single-mode fiber strand, significantly reducing fiber cabling resources. CWDM SFPs must be used with CWDM passive multiplexers, demultiplexers, or optical add/drop. In general, CWDM SFPs come in eight wavelengths that range from 1470 nm to 1610nm.
multiplexers (OADMs).

DWDM SFP

The DWDM SFP is another WDM optical transceiver that uses DWDM technology. Compared with CWDM SFPs, the DWDM SFP enables the transmission of up to 61 channels on a single-mode fiber strand, significantly reducing fiber cabling resources. DWDM SFPs must be used with DWDM passive multiplexers, demultiplexers, or optical add/drop multiplexers (OADMs).

PON SFP

PON SFP optics are utilized in the Central Office’s Optical Line Terminal (OLT) and the Subscriber’s Optical Network Terminal/Unit (ONT/ONU). PON can be broken down into GPON SFP and EPON SFP optics. It is mainly for FTTX applications.

BiDi SFP

The BiDi SFP optics is a compact, hot-swappable optical transceiver that transmits and receives data across a single fiber. BiDi optical transceivers, as opposed to ordinary optical transceivers, use WDM duplexers to mix and isolate data sent over a single fiber.

Fiber Channel SFP

Fibre Channel, sometimes known as FC, is a high-speed network technology (typically capable of 1, 2, 4, 8, 16, and 32 Gbps) generally used to link computer data storage to servers. Fibre Channel (FC) is the most widely used technological standard in the Storage Area Network (SAN) data center environment. Fibre Channel SFP is an SFP optical transceiver developed for fiber channel storage applications. It is also referred to as fiber channel SFP and includes 2G FC SFP, 4G FC SFP, and 8G FC SFP.

SONET/SDH SFP

SONET/SDH SFP refers to SFP optics that are suited for SONET/SDH and ATM applications, such as OC-3/STM-1 (155 Mbps) SFP, OC-12/STM-4 (622 Mbps) SFP, and OC-48/STM-16 SFP (2488 Gbps). The SONET/SDH SFP allows multimode, short-reach, intermediate-reach, long-reach (40km), and long reach (80km) applications.

SDI Video SFP

SDI Video SFP refers to SFP optics that support 12G-SDI, 6G-SDI, 3G-SDI, HD-SDI, or SD-SDI. It is a special SFP for broadcast video transport with high-capacity HD and ultra-high-definition (UHD) digital transmission. Unlike the commonly used SFP, this video SFP transceiver can support the SDI video pathological signal while also ensuring video transmission quality. The video SFP market is small, so few suppliers provide SDI video SFP optics.

Conclusion

Figure out what your network technology is and what devices and cables are in your system, further increase the transmission speed to match the form factor, and the transmission distance to choose a single-mode or multi-mode SFP with the desired range. Consider cabling infrastructure for the correct SFP connector type, and keep these SFP optics buying factors in mind the next time you buy a new SFP transceiver.
If you need to use the module in harsh environments with extreme temperatures, give priority to industrial SFPs. Choose a reliable supplier that ensures device compatibility. Don't forget the SFP DOM functionality. Each optic has unique capabilities that provide different parameters depending on what you're switching and network requests. Remember to choose the most suitable SFP, not the most expensive SFP.

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