Fiber optics are primarily employed for data transmission due to their efficiency and high capacity. They are typically categorized into two main types: multimode fiber (MMF) and single-mode fiber (SMF), distinguished by their transmission modes. An essential difference between them lies in the transmission distance they can accommodate. Fiber mode conversion becomes necessary when optimizing distance in optical applications.
Learn About Multimode vs Single-mode Fiber
Multimode fiber (MMF) and single-mode fiber (SMF) are two types of fiber optic cables utilized for transmitting light signals over extended distances (For details, please refer to the blog post “Choosing the Right Fiber Optic Cable: Singlemode vs Multimode“). The primary distinction between them lies in the size of their fiber cores and the compatible devices. The core size plays a crucial role in determining the distance over which a signal can travel without experiencing distortion. Generally, the larger the core size, the shorter the achievable distance. This characteristic makes multimode fiber more suitable for indoor applications.
1. Multimode Fiber (MMF):
As implied by its name, multimode optical fiber simultaneously carries multiple light rays at varying speeds and reflection angles due to its larger core diameter. Typically, the core diameter of multimode fiber ranges from 50 to 62.5 microns, making it suitable for premises applications with data rates of up to 10 Gbps. Multimode fiber (MMF) is ideal for transmitting data over shorter distances while providing high bandwidth at high speeds.
However, exceeding the distance limit of multimode fiber can lead to attenuation, resulting in a loss of signal strength. This attenuation can cause errors in the transmitted data, potentially leading to data corruption or loss. The distance limit for multimode fiber is influenced by the fiber’s quality and the type of signal being transmitted. Generally, the longer the distance of the multimode fiber, the greater the attenuation.
2. Single-mode Fiber (SMF)
Single-mode fiber (SMF) is a type of optical fiber consisting of a single strand of glass fiber. It facilitates the transmission of data over long distances at higher speeds, emitting only a single ray of light at any given time. The core diameter of single-mode fiber typically ranges from 8 to 9 microns, making it smaller than multimode fiber (MMF). SMF is predominantly employed in longer-distance applications, supporting data rates of up to 100 Gbps.
Utilizing laser light, single-mode fiber is more expensive than multimode fiber. It serves to connect devices across extended distances. The maximum distance achievable with single-mode fiber is approximately 140 kilometers.
When is Multimode to Singlemode Conversion Necessary?
Multimode to single-mode conversion is necessary under the following circumstances:
1. Connectivity between multimode equipment within a building and a single-mode network outside is required.
2. Legacy equipment utilizes LC and SC ports with fixed multimode fiber, but there’s a need for connectivity to single-mode equipment.
3. The cost of proprietary single-mode SFPs is high, leading to increased expenses.
4. The goal is to link multimode network equipment to a single-mode CWDM multiplexer.
Method For Converting Multimode Fiber to Single-mode Fiber
To achieve multimode to single-mode fiber conversion, there are three common methods:
1. Fiber-to-Fiber Media Converter for MMF-to-SMF Fiber Conversion
This converter facilitates extending a multimode network over single-mode fiber, covering distances of up to 160km cost-effectively. For instance, a 550m/20km 850nm/1310nm SFP Gigabit Ethernet MMF to SMF converter can support mode conversion from multimode fiber (up to 550 m) to single-mode fiber (up to 20 km) for Gigabit Ethernet (1000 Mbps) transmission.
In practical applications involving extending fiber network distances, two Ethernet switches equipped with multimode fiber ports can be connected using a pair of multimode to single-mode converters. These converters transform the multimode fiber to single-mode fiber, enabling network connectivity across the distance between the switches.
2. WDM Transponder for MMF-to-SMF Fiber Conversion
Similar to a multimode to single-mode fiber converter, a WDM transponder is another solution for converting multimode to single-mode fiber. As implied by its name, a transponder is commonly employed in WDM (Wavelength Division Multiplexing) systems, particularly in DWDM (Dense Wavelength Division Multiplexing) systems. This is because, in long-distance DWDM transmission, conversions between MMF and SMF are often necessary.
In the provided example, the WDM transponder is equipped with two ports: one fitted with a single-mode SFP and the other with a multi-mode SFP. An OM3 MMF is utilized to link the multi-mode port of the WDM transponder to the multi-mode port of the switch. To extend connectivity between buildings, the single-mode OS2 fiber is used to connect the SMF SFP ports of the WDM transponder.
3. Mode Conditioning Fiber Cable for MMF-to-SMF Fiber Conversion
In contrast to the previously mentioned methods, mode conditioning fiber cable offers a different approach to converting between multimode and single-mode fiber. Unlike the WDM transponder, which converts signals into electrical ones, mode conditioning patch cable achieves conversion by launching the laser at a precise offset from the center of the multimode fiber.
This deliberate offset causes the laser to spread across the diameter of the fiber core, thereby mitigating the effects of differential mode delay (DMD). DMD occurs when the laser couples onto only a small number of available modes in multimode fiber, leading to signal degradation.
It’s important to note that mode conditioning fiber cable is primarily utilized in applications that employ Gigabit 1000BASE-LX equipment, as well as 10-Gigabit Ethernet 10GBASE-LRM and 10GBASE-LX4 equipment.
Considerations for Fiber Mode Conversion
1. Fiber Type
Single-mode and multimode fibers possess different core diameters and support distinct transmission distances. Selecting the appropriate fiber type that aligns with the application and is compatible with the connected equipment is crucial.
2. Connector Type
Single-mode and multimode fibers utilize different connector types. Ensuring compatibility between the connectors at both ends of the fibers is essential. Fiber optic connectors, such as SC, LC, FC, and ST, are employed to link fiber optic cables with network switches, media converters, and transponders. Understanding the connector type used in the network equipment and cable is vital.
3. Wavelength
The wavelength of light employed for data transmission over the fiber can impact its performance. Single-mode and multimode fibers operate at different wavelengths. It’s imperative to confirm that the wavelengths are harmonious with each other.
4. Cost
Fiber type conversion can incur expenses, but it often proves more cost-effective compared to alternatives such as replacing existing fiber or network equipment. Utilizing a media converter to convert from single-mode to multimode fiber is usually a quicker and more economical solution.
5. Standards and Regulatory Compliance
Adhering to industry standards and regulations is essential for ensuring safety, compatibility with other equipment, and compliance with government requirements. Confirming that the conversion process aligns with established standards is crucial.
Conclusion
Fiber mode conversion becomes necessary to establish connectivity between multimode and single-mode fiber cables, or to interface a multi-mode fiber cable with a device designed to accept single-mode wavelengths (or vice versa). In addition, we also provide Optical Transceiver Modules and high-quality fiber optic patch cords and patch panels to help you deploy your network in the most cost-effective manner.
