The Impact of SWDM over Multimode Fiber

Networks require infrastructure that can handle enough data to meet our everyday needs. One technology getting a lot of coverage is wideband multimode fiber (WBMMF). James Donovan explains how network operators can learn how short wavelength division multiplexing and WBMMF can work together and support future applications.

Single_Fiber_WBMMFMultimode fiber cabling is the workhorse media of local area network (LAN) backbones and data centers. It offers the lowest cost means of transporting high data rates for the needed distances. Multimode fiber evolved from being optimized for multi-megabit per second transmission using light emitting diode (LED) light sources, to being specialized to support multi-gigabit transmission using 850 nm vertical cavity surface emitting laser (VCSEL) sources.

Channel capacity has also been multiplied through the use of parallel transmission over multiple strands of fiber. These advances have increased multimode supported data rates by an astounding factor of 40,000—from 10 Mb/s in the late 1980s to 100 Gb/s in 2010, with 400 Gb/s in development in 2015.

While parallel transmission is simple and effective, the more optical lanes used drives higher cost into the cabling system. Shortwave wavelength division multiplexing (SWDM) takes advantage of another means of multiplying data rates using multiple wavelengths to increase the capacity of each fiber by at least a factor of four. This enables at least a four-fold increase in data rate for a given number of fibers (possibly enabling 1600 Gb/s) or at least a four-fold reduction in the number of fibers for a given data rate (enabling 100 Gb/s per fiber).

With SWDM, wavelengths are used in the lower cost, short wavelength range around 850 nm to add lanes within a single strand of optical fiber. Using more wavelengths improves the use of the multi-mode fiber, expanding its information carrying capacity; however, using SWDM on existing fibers is going to be limited in terms of the bit rates or the distances that can be achieved, because those fibers were designed primarily to operate at one wavelength of 850 nm.

Optimized to support wavelengths in the 850 nm to 950 nm range to take advantage of SWDM, wideband multimode fiber (WBMMF) ensures not only more efficient support for future applications to useful distances, but also complete compatibility with legacy applications, making it an ideal universal medium that supports not only the applications of the present, but also those of the future.

Want to know more about the details of SWDM and WBMMF? The CommScope Infrastructure Academy has a 40-minute tutorial (WR9440 Wideband Multimode Fiber) that illustrates the technical aspects of multiplexing techniques over fiber and the enhancements made to achieve the WBMMF specification.

Taken together, shortwave division multiplexing and wideband technologies are going to extend the use of multimode fiber, continuing the legacy of delivering lowest cost optical solutions over the universal data transmission media that is multimode fiber.