Multi-mode Fiber vs. Single-mode Fiber vs. Copper Cable, A Battle That Never Wins OR Loses

Preface

In the field of network infrastructure, there are three technologies that do not distinguish between high and low: copper cable, single-mode fiber and multi-mode fiber. In this protracted “war”, there may never be a clear winner. The reason is that the three technologies have their own advantages, and these technologies complement each other, although some suppliers may always instill in customers One of the best views of a certain product to promote their most profitable technology, but most network infrastructure decision makers are well aware that only a combination of the three is the wisest.

Similarity

The basic design of optical cables is composed of at least two different optical materials. Both single-mode and multi-mode optical fibers are optical waveguides. The optical signal cladding layer is contained in the “glass” core. Most of the cladding layer has the same crystal structure, but with different doping methods (for example, the ratio of boron to germanium is variable).

✦Fiber core: The central fiber layer of the fiber, where light is transmitted.

✦Cladding: The outer optical layer confines the light in the core and guides it to transmit.

✦Buffer coating: Hard plastic coating can protect the glass from moisture or physical damage.

The optical fiber is based on the principle of total internal reflection: the light propagating in the fiber core will be reflected back into the core when it reaches the boundary between the cladding and the core. The optical signal propagates in the core layer of the optical fiber, but the propagation mode varies with the type of optical fiber.

The geometric factor largely depends on the size of the core: all types of fibers have an outer diameter (cladding size) of 125 microns. They differ in the size and structure of the core. The large diameter core of 62.5 and its larger numerical aperture (NA) make it the best choice for LED-based systems because it can collect more light from the larger emission patterns of typical LEDs. The 50-micron size LED is less efficient, but the narrow emission width of the VCSEL (laser diode) can also be perfectly coupled to 50 and 62.5 microns. The low light collection capacity of 50 microns means that it carries fewer modes, so the overall bandwidth is higher than 62.5. This has been brought to the extreme in single-mode fiber.

 

How to choose? Depends on demand

✦If you need a longer transmission distance, you will choose a single-mode system.

✦If you do not need to support long-distance links, for example, you do not need any links longer than 550 meters, and want to limit the total system cost (including active equipment), you can choose multimode fiber;

✦Multimode fiber supports high data rate applications (the speed is the same as single mode, but the distance is shorter);

✦Multimode fiber optic system is easier to maintain and keep clean than single mode. Contamination (such as dust) at the connector interface is a headache for any fiber optic system operator, but the connector interface of a multi-mode fiber optic system is less sensitive to dust than a single-mode system. On the other hand, copper cable interfaces are generally not susceptible to such pollution interference.

 

Six reasons for choosing multimode fiber (MMF)

01 Distance

According to the expected application range, the distance supported can reach up to 440 meters.

02 Maintenance

Compared with single-mode fiber, multi-mode fiber has a larger core diameter and higher positioning tolerance, so it is easier to maintain and keep the connector interface clean.

03 Cost

Link costs include integrated wiring components and transceivers. The best option is a combination of multimode fiber and multimode transceivers, which may provide an attractive low-cost option. When the distance exceeds the capability of multi-mode fiber, single-mode fiber will replace multi-mode fiber.

04 Standard

OM3 is generally considered to be the most basic option at the moment. With the emergence of new and higher-speed applications, the limitations of OM3 are beginning to appear-it may force the transmission distance to be shortened, resulting in the inability to support the scale required by the data center. For many people, this is not a suitable long-term option.

 

05 Daily Choice

OM4 is a commonly used standard today. It provides a higher bandwidth (capacity) than OM3, so OM4 is a typical recommended option for new applications.

06 Multiple Wavelengths

The industry now has the ability to use multiple wavelengths on MMF (SWDM), similar to WDM on SMF. This is a significant increase in MMF capacity. Here, the combination of multiple wavelengths can increase the capacity by 4 times (SWDM4 protocol). CommScope is the first to introduce OM5, which aims to complement SWDM to provide higher bandwidth-which means longer transmission distances for more wavelengths. OM5 is a future-oriented standard.