Tag: WDM

5G Is Driving the Evolution of Optical Transceiver Industry

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We are now starting to see commercial 5G networks going live. Previous generations were focused on consumer and personal communications but now 5G will serve consumers, enterprises and take the internet of things to the next level, where superior connectivity is a prerequisite. Initially, 5G will be a capacity enhancer in metropolitan areas and enhanced mobile broadband and fixed wireless access will be ways for operators to address explosive traffic growth.

According to LightCounting, 5G will drive significant growth in the global market for optical transceivers since 2019, especially in China. At the same time, the demand for low-speed optical devices below 10G will gradually decrease and increase in the demand for transceivers of 25G, 50G, and 100G.

The change of optical transceiver demand is driven by 5G revolution. RAN architecture of the 5G system will realize the separation of CU and DU, which determines that 5G wireless network will include fronthaul, midhaul and backhaul. New requirements are proposed in terms of the amount of optical transceiver and the technical requirements of the optical transceiver.

Optical transceivers Need to Be Able to Meet the Requirements for Bearer Network in 5G Era

Fronthaul

The transmission distance should be within 10km or even shorter. The operating temperature should reach industrial temperature and the CPRI interface rate should reach 25Gbps.

Midhaul

The transmission distance should be at least 10km and the operating temperature should reach the commercial temperature. Gray optical transceiver or BiDi is mainly considered. In addition, 50G PAM4 may be a good choice.

Backhaul

The transmission distance should be more than 10km and the operating temperature should reach the commercial temperature. The 100G, 200G, 400G rate optical transceiver is mainly used. In addition, WDM or coherence technology will be taken into consideration.

 

Since the evolution of CPRI interface to PRI will lead to an increase of RRU power consumption, more heat-resistant optical transceivers are needed. In addition, the wireless architecture will evolve from DRAN to CRAN, and there will be a shortage of optical cable resources, which requires more energy-saving optical transceivers. In addition, 5G will use a higher frequency band, the coverage will be smaller, and the number of optical transceivers will be greatly increased so that the low-cost optical transceivers are needed. At the same time, 5G’s spectrum bandwidth increases transmission bandwidth, and higher speed optical transceivers are needed to meet this demand.

Conclusion

All in all, the core requirements for optical devices in wireless scenarios are mainly reflected in higher operating temperature range, less fiber resource consumption, lower cost, and faster single wave rate.

 

How to meet these needs of optical transceivers in the 5G era?

The solutions for High-temperature transceiver — industrial temperature light chip and silicon light can make the optical device itself work at high temperature, and can guarantee rapid heat conduction through good thermal design.

The solutions for optical fiber resource shortage—the most obvious solution is to use BiDi, which can save 50% of the optical fiber resources and thus use the existing optical fiber resources to transmit twice the bandwidth. Passive WDM solutions are also available.

 

Building on the success of the company’s 10G CWDM SFP+

transceiver and 10G DWDM SFP+ transceiver, Gigalight developed its next-generation 25G CWDM  in an SFP28 form factor. And Gigalight 25G SFP28 BiDi optical transceivers are available. This technology is believed to be a key building block for deploying these transceivers and is designed to enable cost-effective next-generation 5G wireless build-outs while also providing significantly more data capacity per fiber than other 25Gbased optical architectures. This will enable Transceiver-to-transceiver communications and self-wavelength tuning of remote transceivers during commissioning without host interaction, so field installation and remote maintenance are simplified and operational expenses are lowered.

 

According to different scenarios, there are different requirements for optical transceivers. The traditional optical device technology in the field can meet the current needs, but there is a trend to update the technical field of evolution. At the same time, the realization path of the growth of optical transceiver rate also presents a diversification trend. Finally, no matter what you need are, Gigalight is here to create, assist and innovate.

WDM Technology Will Be Broadly Used in the Coming 5G

 

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An Overview of WDM

WDM stands for Wavelength Division Multiplexing. WDM is the most important and most popular method to increase the capacity of a single strand of fiber.  

Traditionally, only one colored light was used on a single strand of fiber to carry the information, such as 1550nm light. However, starting from the early 1990s, the Internet boom pushed service providers to find a method to increase the capacity on their network in the most economical way. That is when WDM devices were invented.

In a WDM system, many different colored lights are combined by a WDM multiplexing device and put into a single strand of fiber, each color is called a channel.

On the receiver side, each color is separated into its own channel by a WDM de-multiplexing device. It shows that a single fiber’s capacity is increased by 40 times with a 40 channel WDM. The beauty of WDM is that you only need to upgrade the end equipment, no need to dig up trenches to bury more fibers, which is much more costly.   
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Communication systems are designed differently, and the width of the gap between each wavelength varies. Depending on channel spacing, WDM can be subdivided into CWDM and DWDM.

CWDM and DWDM

CWDM supports up to 18 wavelength channels transmitted through a fiber at the same time. To achieve this, the different wavelengths of each channel are 20nm apart.

DWDM, supports up to 80 simultaneous wavelength channels, with each of the channels only 0.8nm apart. 

CWDM technology offers a convenient and cost-efficient solution for shorter distances of up to 70 kilometers.

For distances between 40 and 70 kilometers, CWDM tends to be limited to supporting eight channels. Unlike CWDM, DWDM connections can be amplified and can, therefore, be used for transmitting data much longer distances.

 

  • Wavelengths Used in WDM

 

DWDM is typically limited to 1450 to 1650nm

CWDM may operate over the full range of 1280 to 1650nm

 

  • Laser Source Spacing

 

DWDM uses lasers at ~0.8nm spacing

CWDM uses lasers at a 20nm spacing  

Advantages of WDM Technology

  1. Large transmission capacity can save valuable optical fiber resources. For single-wavelength optical fiber systems, a pair of optical fibers are needed to transmit and receive a signal, while for WDM systems, no matter how many signals there are, the entire multiplexing system only needs a pair of optical fibers. For example, for 16 2.5gb /s systems, the single-wavelength optical fiber system needs 32 optical fibers, while the WDM system only needs 2 optical fibers.
  2. It can transmit different types of signals such as digital signals, analog signals, etc., and can synthesize and decompose them.
  3. When the network capacity is expanded, there is no need to deploy more optical fiber, nor need to use high-speed network components, only need to change the end machine and add an additional wavelength of light to introduce any new service or expansion capacity, so WDM technology is an ideal means of capacity expansion.
  4. The dynamic reconfigurable optical network can be constructed, and the all-optical network with high flexibility, high reliability, and high survivability can be formed by using optical division multiplexer (OADM) or optical cross-connection device (OXC) at the network nodes.

WDM Technology Is Expected to Optimize Cost for 5G Development

The 5G wireless infrastructure necessitates wavelength division multiplexing (WDM) technology to optimize fiber usage. Fixed and reconfigurable multiplexing are two approaches that provide tradeoffs in terms of network scalability, reliability, and cost. Optical networks closest to the antenna are the most cost sensitive and can benefit from fixed WDM solutions. Gigalight’s broad portfolio of WDM modules is available in various configurations including coarse-WDM (CWDM), dense-WDM (DWDM) modules and other WDM solutions.