Single-mode vs. Multi-mode Transceiver

We are quite familiar with difference between single-mode fiber (SMF) and multi-mode fiber (MMF), but we know little about single-mode and multi-mode transceiver. So what are they? And how to choose between them. Actually single-mode and multi-mode fiber are the transport media of a transceiver module. Besides this, here are certain things you need to know before making that decision which can prevent additional costs in the future.

The key differences between single-mode and multi-mode transceiver lie in the following expects—distance and cost, speed, how they work and compatibility issue. The following text will explain them one by one.

Distance and Cost
The single-mode fiber based transceivers work mainly in 1310nm and 1550nm wavelength and have a transmission distance of 2 km to 120 km. While multi-mode fiber based transceivers work in 850nm wavelength and are only used for short distance defined from 150 meters to 5 kilometers. The difference in transmission distance is owing to different transmitter power, receiver sensitivity and the wavelength in operation.

The cost difference between single-mode and multi-mode transceiver mainly arises from the cost difference between single-mode fiber and multi-mode fiber. It is known that the optic for single-mode is nearly twice the cost of multi-mode fiber. But the cost of a single-mode transceiver is negligible when installed as part of a project. Therefore, multi-mode transceivers are typically used when the distance involved is not long.

Speed
Both single-mode transceiver and multi-mode transceiver can transmit 10G speed. You just need to consider the distance requirement. Multi-mode can only support 300 to 400 meters. Single-mode transceiver can support link lengths up to 120 km. But prices go up accordingly.

How They Work
Single-mode fiber has a smaller core (9 micron) and narrower wavelength, which means that SMF has the capability for higher bandwidth and much longer distances in transmission. And because of its smaller core, single-mode fiber has less light diffraction over distance than multi-mode fiber (50, 62.5 micron). That’s the reason why single-mode transceiver can support link length up to 120 km. Figure 1 shows a compatible Cisco GLC-LX-SM-RGD and a single-mode patch cable.

 

In contrast, multi-mode fiber has a much bigger core and uses a longer wavelength of light, resulting in MMF having higher numerical apertures which means they are better at collecting light than single-mode fibers. In fact, this refers to the optics is cheaper. Due to the modal dispersion in the fiber, multi-mode fiber has higher pulse spreading rates than single mode fiber, limiting multi-mode fiber’s information transmission capacity. Thus multi-mode transceiver can only support shorter distance. Figure 2 shows a compatible Cisco GLC-SX-MMD and a multi-mode patch cable.

Compatibility Issue
Can I use single-mode fiber over multi-mode transceiver or vice versa? This is the question we have heard so many times from our customers. The answer is not that easy.

We all knew that single-mode fiber and multi-mode fiber are not compatible. The main reason is that they possess distinct wavelength of the laser and core size of the fiber. Take Cisco SFP as an example, there is a type of SFP transceiver module (GLC-LX-SM-RGD) which can support both single-mode and multi-mode fiber. But a mode conditioning patch cable is always required when using single-mode transceiver (like GLC-ZX-SMD) with 62.5-micron MMF, and only at distances that would have worked using multi-mode transceivers. It does not work when we are exceeding the distance specified for multi-mode fiber. The result could be an elevated bit error rate.

Summary
When we choose between single-mode transceiver and multi-mode transceiver, we must take all the above factors into consideration. Budget of course is the number one factors considered by many users. To save more, we are able to choose the compatible modules without sacrificing any quality or reliability but only with a low cost. Fiberstore supplies compatible fiber optic transceiver modules of many brands, such as Cisco, HP, Juniper, Brocade, Finisar etc. You are welcomed to contact us for more information.

Basic Information About SFP Transceiver Modules

SFP (small form-factor pluggable) transceivers, as one of the most useful technological advancements on the market are warmly welcomed by subscribers. These transceivers are some of the most reliable devices in the market because the designs are derived from a multi-source agreement (MSA) and are a pluggable form of SFF. They are hot-swappable, which is highly beneficial to designers in the industry. Besides these helpful information, here are some things you need to know about SFP transceiver modules.

Types of SFP Transceivers
SFP transceivers are available with a large amount of transmitter and receiver types. Customers can select the appropriate transceiver to provide the required optical reach over multi-mode fiber (MMF) or single-mode fiber (SMF).

Optical SFP module is commonly offered in several different categories: SX, LX, ZX, 1000BASE-T, and DWDM, etc. Each category supports a different distance that will transmit data both upstream and downstream. For instance, the SX model will transmit for 10 km, ZX will transmit up to 80 km and DWDM transceiver will achieve various distance at various wavelengths. Take Cisco SFP as an example.

• For copper twisted pair cabling

Cisco 1000BASE-T SFP module (Cisco GLC-T) operates on category 5 unshielded twisted-pair copper cabling of link lengths up to 100 m.

• For multi-mode fiber

GLC-SX-MMD operates on 1000BASE-SX standard links up to 550 m

• For single-mode fiber

GLC-LH-SMD 1310 nm, for distances up to 10 km
GLC-EX-SMD 1310 nm, for distances up to 40 km
GLC-ZX-SMD 1550 nm, for distances up to 80 km

Where Transceivers Are Used?
Most SFP transceivers can be found in popular networking systems such as Wide Area Networks (WANs), Metro Access Network, and Metro Core Network. SFP transceivers support fiber networking standards such as Fibre Channel, SONET, and Gigabit Ethernet. They also support a variety of other communications standards as well. A compact and hot-swappable optical transceiver can be used in all types of optical communications and telecommunications applications. These devices will connect a switch, router, or other network device.

Advantages of an SFP Transceiver
SFP transceiver is hot-swappable, which make it easy to change and easy for maintenance compared with traditional modules. SFP transceiver modules make the fiber optic network or fiber-Ethernet network easier to upgrade or maintain users can replace a single SFP module during the process instead of replacing the whole board with many modules on it.

Digital optical monitoring (DOM) is based on the new and modern optical transceiver design. Consumers have the ability to monitor real-time parameters of the SFP module. Optical inputs and output power, laser bias, and supply voltage will allow designers to monitor real-time.

In addition, A SFP transceiver is capable of transferring data rates up to 4.25 Gpbs. The XFP form factor is similar to the SFP type. But compared to XFP (10 Gigabit Small Form Factor Pluggable) transceiver, the functionality of SFP module increases about three times at 10 Gpbs. SFP transceivers have a higher optical reliability and will permit higher soldering temperatures. SFP transceivers are recommended by fiber optic component providers to ensure proper data transmission.

Conclusion
SFP modules are some of the best in the industry and will ensure that your design operates at full capacity with low failure rates. This article mainly analyzes three expects of SFP transceiver modules, namely the category of SFP module, application and advantage. Fiberstore offers an exceptional amount of SFP modules that are fully compatible with major brand (Cisco, HP, Finisar, Juniper, etc.). Not only GLC-SX-MMD, GLC-ZX-SMD, DS-SFP-FC8G-SW and EX-SFP-1GE-SX, but also GLC-T SFP are all available in Fiberstore. I cannot list all the compatible SFP transceivers here. If you are interested, you can contact us directly.