Tag Archives: SWDM

Wideband Multimode Fiber: What to Expect From It?

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Multimode fiber (MMF) holds a major position in local area network (LAN) backbone cabling and data center due to its capability to transmit high data rates at relatively low cost. MMF has evolved now to support multi-gigabit transmission using 850 nm VCSEL (vertical cavity surface emitting laser) sources, and the channel capacity of which is greatly improved with the use of parallel transmission over multiple strands of fiber. Wideband multimode fiber (WBMMF), known as OM5, lately comes into our horizon as an alternative to support the escalating data rate and higher bandwidth. Then what can we expect from using WBMMF? This article may give you some hints.

Existing Problems of Multimode Fiber

OM1 and OM2 MMF are developed with the intention to support Fast Ethernet, which fail to support 10 Gbps and 25 Gbps data transmission rates. Hence they are not suggested for new installations. Laser-optimized OM3 and OM4 MMF now play a dominant role in 10G, 40G and 100G Ethernet cabling. However, the demand for bandwidth accelerates so fast, and the VCSEL-based transceiver technology cannot keep pace. Consequently, it’s getting more costly for fiber cabling systems to support next-generation Ethernet migration.

Wideband Multimode Fiber: Taking New Wavelength to Multimode Fiber

Wideband multimode fiber (WBMMF) is designed to carry multiple short wavelength signals that can be aggregated for high bandwidth applications–—a technology known as wavelength division multiplexing (WDM). Unlike conventional multimode fiber that optimally supports a single wavelength, WBMMF can accommodate multiple wavelengths, enabling these multiple wavelengths to simultaneously travel along a single fiber strand.

wideband multimode fiber

In this way, WBMMF increases each fiber’s capacity by at least a factor of four, allowing at least a fourfold data-rate increase, or a fourfold reduction in the number of fibers. That means, when transmitting four optical signals, instead of using four separate fibers, WBMMF can send down these signals on one fiber over four separate operating windows. For example, 400GbE could be accomplished with 4Tx and 4Rx fibers (today 400GbE over multimode requires 16Tx and 16Rx fibers).

Highlights of Wideband Multimode Fiber

So, what makes WBMMF standing out from other multimode fibers? Besides that it increases MMF’s utility and extends MMF’s value to customers, WBMMF also has the following advantages:

    • WBMMF can support wavelength division multiplexing (WDM) across the 840-953nm wavelength range, at 30nm intervals.

WBMMF wavelength

  • The fiber geometry of WBMMF stays the same as existing OM4 fibers, therefore it is backward compatible with OM4 multimode fiber at 850 nm, making it feasible to retain legacy application support of OM4.
  • WBMMF reduces fiber count by a faction of four, but increases capacity to over 100 Gb/s per fiber, enabling Ethernet 100G-SR, 400G-SR4, 1600G-SR16 and Fiber Channel 128G-SWDM4.
Applications of WBMMF: Short Wavelength Division Multiplexing (SWDM)

WBMMF provides better performance for applications using WDM technology. As the parallel multimode fiber MPO cabling is considerably more costly than the multimode fiber LC-duplex patch cord, WBMMF made it possible to use a single pair of LC fiber instead of MPO trunks in direct point-to-point connection. Which helps to reduce fiber count by transmitting multiple wavelengths in the same multimode fiber, and to keep the overall cabling costs to the minimum.

WBMMF and SWDM

Conclusion

Wideband multimode fiber is a reliable medium to expand your data center or enhance network capacity. With the capability of managing multiple wavelengths, it effectively reduces the number of fibers and enhances total channel capacity, proven to be a cost-effective solution for increasing network bandwidth, and to keep pace with the escalating data demands.

WBMMF – Next Generation Duplex Multimode Fiber in the Data Center

Enterprise data center and cloud operators use multimode fiber for most of their deployments because it offers the lowest cost means of transporting high data rates for distances aligned with the needs of these environments. The connections typically run at 10G over a duplex multimode fiber pair—one transmit (Tx) fiber and one receive (Rx) fiber. Upgrading to 40G and 100G using MMF has traditionally required the use of parallel ribbons of fiber. While parallel transmission is simple and effective, continuation of this trend drives higher cost into the cabling system. However, a new generation of multimode fiber called WBMMF (wideband multimode fiber) is on the way, which can enable transmission of 40G or 100G over a single pair of fibers rather than the four or ten pairs used today. Now, let’s get close to WBMMF.

What Is Wideband Multimode Fiber?
WBMMF is a new multimode fiber type under development that will extend the ability of conventional OM4 multimode fiber to support multiple wavelengths. Unlike traditional multimode fiber, which supports transmission at the single wavelength of 850 nm, WBMMF will support traffic over a range of wavelengths from 850 to 950 nm. This capability will enable multiple lanes of traffic over the same strand of fiber to transmit 40G and 100G over a single pair of fibers and to drastically increase the capacity of parallel-fiber infrastructure, opening the door to 4-pair 400GE and terabit applications. Multimode fiber continues to provide the most cost-effective platform for high bandwidth connectivity in the data center, and with the launch of the WBMMF solution, that platform has been extended to support higher speeds with fewer fibers and at greater distances.

Wideband Multimode Fiber

What Is the Technology Behind WBMMF?
WBMMF uses short wavelength division multiplexing (SWDM) to significantly increase its transmission capacity by four times. WDM technology is well known for its use in single-mode transmission, but has only recently been adapted for use with vertical cavity surface-emitting lasers (VCSELs), which have been proven in high-speed optical communications and are widely deployed in 10G interconnection applications. SWDM multiplexes different wavelengths onto duplex MMF utilizing WDM VCSEL technology. By simultaneously transmitting four VCSELs, each operating at a slightly different wavelength, a single pair WBMMF can reliably transfer 40G (4x10G) or 100G (4x25G). The use of SWDM then enables WBMMF to maintain the cost advantage of multimode fiber systems over single-mode fiber in short links and greatly increases the total link capacity in a multimode fiber link.

SWDM WBMMF

Why Does WBMMF Make Sense?
In order to increase transmission speeds up to 10G or 25G, transceiver vendors simply increased the speed of their devices. When 40G and 100G standards were developed, transmission schemes that used parallel fibers were introduced. This increase in fiber count provided a simple solution to limitations of the technology available at the time. It was accepted in the industry and allowed multimode links to maintain a low cost advantage. However, the fiber count increase was not without issues. At some point, simply increasing the number of fibers for each new speed became unreasonable, in part because the cable management of parallel fiber solutions, combined with the increasing number of links in a data center, becomes very challenging. Please see the picture below. Usually, 40G is implemented using eight of the twelve fibers in an MPO connector. Four of these eight fibers are used to transmit while the other four are used to receive. Each Tx/Rx pair is operating at 10G. But if we use WDMMF, two fibers are enough. Each Tx/Rx pair can transmit 40G by simultaneously transmitting four different wavelengths. This enables at least a four-fold reduction in the number of fibers for a given data rate, which provides a cost-effective cabling solution for data center.

Parallel fibers vs WBMMF

Conclusion
WBMMF is born at the right moment to meet the challenges associated with escalating data rates and the ongoing need to build cost-effective infrastructure. Besides, WBMMF will support existing OM4 applications to the same link distance. Optimized to support wavelengths in the 850 nm to 950 nm range to take advantage of SWDM, 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.

Original article source: http://www.fs.com/blog/wbmmf-next-generation-duplex-multimode-fiber-in-the-data-center.html