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Optical communication (also known as optical telecommunication) is a communication technique that relies on optical fibers to carry signals. Traditionally, Optical Communication technology has been employed to provide high capacity backbone communication, however, with the development of low-loss optical fiber cables, optical communications has become one of the most widespread methods of communication. The global market for optical networking and communications is expected to cross $40 Billion by 2024 at a CAGR of 7.6% [1]. The massive growth in wireless network traffic (contributed earlier by 4G and now by 5G networks), and high speed/high performance computing have put new demands and challenges in front of optical communication and photonics technology. The capacity requirement for 5G backhaul networks is expected to rise at-least 10x as compared to 4G networks. Similarly, the link data rate requirement in data centers has been exponentially rising and has reached up to 400 Gbps with expectations to reach Tbps levels by 2021-2022. The next generation optical communication devices are required to be highly flexible, scalable, support high speeds while simultaneously consume less power, occupy less space and remain cost effective.
Nowadays, companies are heavily investing in the R&D to identify new materials which can improve the performance of existing optical communication devices. Graphene, a material which has always been under the research scanner is now being investigated to explore its different applications in the field of optical communication. Chinese academic institutes are at the forefront of conducting active research in this technology area. Two-dimensional (2D) nanomaterials have also emerged as one of the most active research fields. 2D Transition Metal Dichalcogenide (2DTMD) and Black Phosphorus are two of the most prominently studied 2D nanomaterials [2]. Owing to their superior optical and electrical properties, these materials are being researched and used for the production of optoelectronic devices. 2DTMD is emerging as one of the potential alternatives to Graphene due to its wide range of electronic band structure spanning visible and infra-red spectrum. Molybdenum disulfide (MoS2) is one of the most actively researched 2DTMD. Black Phosphorus has different crystal structure and narrower band-gap than 2DTMD and exhibits the property of thickness-dependent direct bandgap. However, high sensitivity of these 2D nanomaterials to external conditions is a challenge which needs to be overcome before they can be used in mass-production of electronic and optoelectronic devices.
Silicon Photonics is a technology area which has drawn the research interest of many companies. In order to achieve bandwidth requirements of modern-day data centers, onboard silicon photonics has been studied for 3D integration using through silicon vias (TSVs) which also helps in reducing power consumption in transceivers [3]. Early deployments of 2.5D integrated-photonic technologies are expected by 2020 before companies start moving to 3D integration [4]. In March 2015, Consortium for On-Board Optics (COBO) was formed to develop standards for interchangeable and interoperable optical modules that can be mounted onto printed circuit boards. The founding members of the COBO include some of the technology giants e.g. Microsoft, Intel, Dell, Juniper Networks, Broadcom [5]. Huawei is another player which is very active in the field of Silicon Photonics. Fiber Bragg Grating (FBG) is another technology area on which there are numerous patents and research papers. FBG is being primarily employed in optical fiber sensors and therefore, most of the research in this field is focused towards sensing application. Silicon Microring is another technology which seems to be in the nascent phase and is yet to get exposed to commercialization. Most of the R&D in the technology is being conducted by academic and research institutes. Silicon microring resonators are used for optical devices such as filters, modulators, delay lines etc. Wavelength selective microring modulators can be used to implement transceivers with ultra-high on-chip bandwidth.is a technology area which has drawn the research interest of many companies. The technology has been is being actively studied and its commercial applications are being explored. Huawei is one of the most active players in this technology area.
The requirement for high speed/high performance transceivers has resulted in active research in the field of laser light source. Vertical-Cavity Surface-Emitting Laser (VCSEL) is the most widely used laser technology at present. However, In-Plane Laser and Comb Laser technologies are being researched to develop high-speed, cost effective, and compact optical transceivers. Coherent transmission is another technology field which is attracting a lot of research interest. In particular, 400G ZR is a coherent 400G Ethernet technology which is being standardized by Optical Interconnect Forum (OIF). 400G ZR provides a cost effective, less complex solution for coherent interconnection with distances up to 120kms while enabling interoperability of coherent interfaces. Recently, Huawei showcased its research on 400G ZR which extended the reach of 400G ZR up to 600kms. Earlier, 400G ZR was considered only for data center interconnects but the technology is now being explored for applications in the telecom sector. However, 400G provides much more capacity than required by mobile service operators (MSOs) for 5G fronthaul/backhaul. Therefore, 100G coherent optics is emerging as a potential candidate to replace existing 10G interfaces due to its low cost and low power [6]. Furthermore, coherent optics is seen as the only viable solution for implementing 800G beyond the distance of 2kms.
The technology landscape of optical communication is drastically changing due to rapid growth in need for high speed connectivity. 5G, Cloud computing, Smart cities, Connected vehicles, Internet-of-Things (IoT), Massive machine communications, Augmented reality/Virtual reality (AR/VR) are some of the leading technology advancements which are the core drivers for the development of optical technologies.
References: [1] https://www.globenewswire.com/news-release/2019/02/19/1733925/0/en/Optical-Networking-and-Communication-Market-to-Reach-40-3-Billion-by-2024-P-S-Intelligence.html [2] https://iopscience.iop.org/article/10.1088/1674-1056/26/3/037307 [3] https://www.osapublishing.org/optica/abstract.cfm?uri=optica-5-11-1354 [4] https://www.osapublishing.org/opn/abstract.cfm?URI=opn-29-3-36 [5] http://onboardoptics.org/ [6] https://www.osa.org/getattachment/31d0e743-58c6-4195-a92f-ba0f713e9bb8/OFC_2018_Post-Show_Report.aspx
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