Why Not Using SWDM Technology Over OM5 Fiber?

Although optical parallel transmission is direct, simple and effective to transmit big data, it is not very recommendable as its cabling cost would be very high for the multiple optical lanes. Then what should we do when we need high capacity network for big data transmission? In this post, it is highly recommended to utilize SWDM (shortwave wavelength division multiplexing) technology as a cost effective solution that offers each fiber at least four times higher capacity for meeting our needs. As shown in the following figure, SWDM technology can multiplex at least four short wavelengths in the 850-950nm range over a single strand of duplex OM5 fiber, so that more than four virtual lanes can be created for optical transmission.

Benefits of SWDM Technology Over OM5 Fiber

Undoubtedly, SWDM technology is a cost effective solution for 40G, 100G or even higher connectivity over duplex multimode fiber, especially OM5. With regard to the benefits of SWDM technology, it is shown below:

Transmission Distance–When using SWDM technology for 40G connectivity over OM5 fiber, the transmission distance can be up to 440 m; for 100G connectivity, the transmission distance can be 200 m at most. Besides, SWDM technology can also support 40G connectivity over OM3 and OM4 at lengths up to 250 m and 350m, respectively.

Excellent Design–Firstly, the Full DDM enables five digital diagnostics functions, temperature, voltage, bias current, Rx power, and Tx power. Secondly, the single Tx and Rx ports enable easier operation and measurement. Thirdly, the simple Tx and Rx port design also makes network security appliances easy and fast.

Power Dissipation–Compared to SR4 optic, the SWDM optic has a lower power dissipation for matching the 4x WDM optical architecture with 4x electrical interface. In general, the power dissipation of QSFP+ SWDM4 can be as low as 1.5W, so that QSFP+ SWDM4 can be also used in the applications with QSFP+ SR4 standard.

40G SWDM4 vs 100G SWDM4 vs 100G SWDM2

With the introduction of OM5 fiber, the multimode fiber cabling system becomes much more popular than ever before. To meet the multimode fiber cabling system needs, multimode SWDM transceiver series including 40G SWDM4, 100G SWDM4 and 100G SWDM2 were published in succession, which are less expensive but have more efficient power consumption, compared to singlemode transceivers.

40G SWDM4–It is a typical kind of QSFP+ transceiver, designed with duplex connector, which always works with duplex-LC OM5 fiber. Since SWDM technology is used in this kind of QSFP+ transceiver, a 40G connectivity can be easily achieved with the use of a pair of 40G SWDM4 transceivers and a length of duplex-LC OM5 fiber cable. When the 40G connectivity is working, four 10G signals with different wavelengths (850nm, 880nm, 910nm and 940nm) are multiplexed at the transmitter end, transmitted through the OM5 fiber cable and finally demultiplexed at the receiver end, as shown in the following figure.

100G SWDM4–It is a QSFP28 standard transceiver with duplex connector used for 100G connectivity. Its working principle is very similar to 40G SWDM4 that can be easily learned from the figure below. In simple words, the total 100G connectivity is done by multiplexing four 25G signals with the same four wavelengths (850nm, 880nm, 910nm and 940nm) over duplex -LC OM5 fiber cable.

100G SWDM2–Compared to 100G SWDM4, the 100G SWDM2 transceiver has a easier working principle which only multiplexes two different wavelengths (850nm and 910nm) for carrying two 50G signals over the duplex -LC OM5 fiber cable. Hence, a 100G connectivity can be totally reached.

Uncertainty of SWDM Technology Over OM5 Fiber

Although the SWDM technology over OM5 fiber brings us so many benefits, there are still some uncertain factors existing that prevent the SWDM technology from being widely adopted. Above all, the SWDM technology is not mature enough to support our needs at present. The factors including SWDM transceiver complexity, the power consumption and the total cabling cost using SWDM technology are the potential obstacles. Meanwhile, the SWDM connectivity is not so flexible as the parallel connectivity and can’t support breakout configuration in the short-reach cabling systems. Once these uncertainty are solved, the SWDM technology will be more and more mature for widely use.

Would You Choose OM5 for Data Center Cabling?

It is recognized that multimode fiber cable (MMF) is always a cost-effective cabling solution for short distance transmission, including OM1, OM2, OM3 and OM4. Nowadays an updated type of multimode fiber cable named OM5 has gained widespread attraction among researcher and specialist in optical communication. Is this kind of MMF cable also a good choice for data center cabling? What are the main differences between OM1, OM2, OM3, OM4 and OM5? Can OM5 perform better than OM4 and other MMF cables? Let’s explore the answers.

OM5 Overview

OM5 is a new 50/125µm multimode optical fiber mainly designed for 40G and 100G data center standardized by TIA and IEC and released in last June. Then in this February, the color of OM5 has also identified, lime green, which is different from that of other MMF cables. Also, the color for OM5 connector and adapter housing should be different for easy identification. However, the OM5 connector and adapter types don’t change which means OM3 and OM4 connector and adapter are still suitable for OM5.

OM5 was initial called wideband multimode fiber (WBMMF) because it specifies a wider range of wavelengths between 850nm and 953nm at the same time for Wavelength Division Multiplexing (WDM) application, while other MMF cables are always used to support one wavelength a time. The WDM technology utilizes OM5 can be called SWDM (the letter S stands for shortwave). Due to this feature, OM5 enables a higher bandwidth network cabling that supports 40G, 100G and beyond.

OM1, OM2, OM3, OM4 vs OM5

As we know, OM1 is the only one 62.5/125um MMF cable always used in 1G application, while OM2 has a smaller core diameter, 50um that supports 1G network at a longer length, 550 m. Different from these two MMF cable mentioned above, 50/125um OM3 is designed to support 10G network at lengths up to 300 m and 40G network at lengths up to 100 m. As for OM4, it came into the market since 2005, as premium OM3. With its help, the 10G transmission link up to 400m and 40G/100G transmission link up to 150m can be achieved.

When it comes to OM5, its core diameter is still 50um and the transmission distance it supports is also the same to that of OM4, as shown in the following table. Then what’s the benefits of OM5, in contrast to the MMF cables mentioned before? Will it supports faster transmission rate? Will it cost less under the same condition? Is it an ideal solution for future-proof network?

OM5 Advantage: Compared to other MMF cables, OM5 supports at least four low-cost wavelengths in the 850-950 nm range, which enables the emerging SWDM applications. As the fiber counts the SWDM application needs is reduced, both higher speed and longer transmission can be achieved by using OM5. In short, OM5 utilizing SWDM technology is able to transmit 40G signals with reach up to 450 m and 100G signals with reach up to 150 m.

OM5 Disadvantage: Firstly, it should cost about 50% more to deploy OM5 cabling, in contrast with the OM4 one, which means OM5 is not an cost effective solution for future-proof network. Moreover, although single-mode fiber OS2, multimode fiber OM5 are feasible for 100/200/400G application, OM5 is still not commonly used due to the short transmission link it can support. Hence, to meet the future-proof network needs, single-mode fiber would be more suitable if high transmission rate and long transmission distance are required.

Conclusion

Currently, OM5 is recommendable for 40G SWDM applications, so that the maximum transmission distance can be extended from 150 m to 450 m. Except for that, there is no any other good reason to recommend OM5 to large data center operators. For example, for migrating to short distance 40G/100G network, OM3 and OM4 apparently offer benefit over OM5; and for migrating to long haul 40G/100G network, single mode fiber is more recommended. We can’t deny that OM5 will bring changes to data center, but there is still a long way to go. We’ll keep up-to-date with OM5 if there is any news updated.