This article address multimode technology trends behind multimode fiber. It explains how cloud and enterprise data centers continue to drive strong demand for multimode solutions, even as transmission speeds increase and SMF transceivers move into the 500-m data space.
Vertical cavity surface emitting lasers (VCSELs) are key enabling devices meeting the requirements of optical interconnects in such data centers up to a few hundred meters of single or multimode fiber due to their simplicity, low cost, and large data transmission rates. Achieving higher bit rates has been the stated goal of research and development during the last years.
With OM4 at a premium over OM3, many data centers and LANs not requiring the extra distance afforded by OM4 continue to deploy OM3 multimode fiber cabling, and it remains more widely deployed for that reason. And while the two fiber types can be mixed due to the same core size, there are some considerations in general when it comes to mixing multimode fiber types.
Since the TIA ratified the specification for OM5, a wideband multimode optical fiber (WB-MMF), customers that are thinking about upgrading their existing infrastructure, or building out new, are asking a question: Should they deploy OM5 fiber? OM5 is essentially an OM4 fiber that has an additional bandwidth specification at 953nm. Both OM4 and OM5 have bandwidths specified as 4,700MHz•km at 850nm, and OM5 has a bandwidth specification of 2,450MHz•km at 953nm. OM4 does not have a bandwidth specified at 953nm. OM5 was designed to be used with optical modules that employ Shortwave Wavelength Division Multiplexing (SWDM). These new SWDM modules use four wavelengths that span from 850nm through 953nm, to implement 100Gbps links.
Over the past several years, Leviton has polled network professionals about the type of fiber they would install today, and we have seen solid growth in single-mode. In the March 2020 poll of 281 network professionals, more than 60% said they would install single-mode (OS2) today over multimode types, with OM4 coming in second at 28%. This change is largely a result of decreasing cost and recent standards committee activities that continue to promote more single-mode options for higher speeds such as 200 and 400 Gb/s. As this trend continues, the market in general will find single-mode a more enticing option. Let’s take a closer look at reasons behind its rise.
Adopted by TIA, the nomenclature for multimode fiber found in the ISO/IEC 11801 standard includes the prefix “OM.” Rather than the spiritual mantra you hear in yoga class, most sources in our industry state that the acronym OM comes from “optical multimode” which seems rather obvious. But when it comes to the various nuances of each type of OM, the differences aren’t quite as obvious. There are currently five types of OM fiber—OM1, OM2, OM3, OM4 and OM5. OM1 fiber was the de facto choice for fiber throughout the 1980s and 1990s, and was still installed into the early 2000s. OM1 has a core diameter of 62.5 µm while OM2, OM3, OM4 and OM5 all feature a 50 µm core.
During the IWCS March webinar, Dr. Earl Parsons of @CommScope compared the return loss of flat and angled MPO connectors with multimode fibers.
Wavefront shaping has revolutionized the spatial control of coherent light beams thanks to the use of spatial light modulators (SLM) in disordered systems such as biological tissue, white paint or multimode fibers. Different approaches have been developed to control the propagation of coherent light that has experienced scattering, such as iterative optimization, optical phase conjugation, and the measurement of the optical transmission matrix.
A new security method – developed for “multimode” glass fibers that can simultaneously carry multiple streams of data – is based on the quantum nature of light. Researchers used “wavefront shaping” to shape the light at the sender’s side so that the receiver gets the desired pattern.
Fiber Optic cabling comes in two basic modes, Single-Mode and Multi-mode. While both modes have different characteristics and serve different purposes, their structural makeup is still the same; an inner core made of purified silica glass, an outer glass known as cladding, and protection by buffer or jacket. For those designing industrial networking systems, a thorough understanding of the differences between single-mode and multimode fiber cabling is vital.