1. Characteristics of Fiber Optic Technology Development
* Evolving Network Demands on Fiber Optics
(1) Increasing transmission capacity per wavelength. Currently, the capacity per wavelength has reached 40 Gbit/s, with research ongoing for 160 Gbit/s. Transmission over 40 Gbit/s imposes specific demands on the polarization mode dispersion (PMD) of the fiber.
(2) Achieving ultra-long-distance transmission. Ideal backbone transmission networks involve relay-free operations. Some companies are now employing dispersion management techniques to achieve 2000-5000 km of electrically relay-free transmission; others use Raman amplification technology to extend the optical transmission distance further.
(3) Adapting to the use of DWDM technology. The current application of 32×2.5Gbit/s DWDM systems has set higher requirements for the non-linear parameters of fibers. ITU-T has finalized the standard (G.650.2) for testing and evaluating the non-linear properties of fibers, specifying effective area requirements and improving the non-linear characteristics of G.655 fibers.
* Emergence of New Fiber Optic Products
(1) New types of high-capacity, long-distance fibers for long-haul communications. Corning’s PureMode PM series, designed for use in 10Gbit/s and above DWDM systems, is well-suited for the development and application of Raman amplifiers. Alcatelcable’s Teralight Ultra fiber has recorded transmission over distances of 100 km and more, with single channel 40 Gbit/s and a total capacity of 10.2 Tbit/s. Some companies have developed fibers with negative dispersion and a large effective area, meeting higher non-linearity requirements and simplifying dispersion compensation schemes, showing excellent results in long-distance unrepeatered transmission and submarine cable communications.
(2) New low-water-peak fibers for metropolitan area network (MAN) communications. In MAN design, there is a need to simplify equipment, reduce costs, and explore the possibility of using non-WDM technology. Low-water-peak fibers extend the bandwidth in the 1360-1460 nm range, optimizing CWDM systems and increasing the transmission channels and distance. Some MAN designs require fibers with low water peaks and negative dispersion to counteract the positive dispersion of optical devices, combining these fibers with G.652 or G.655 standard fibers for dispersion compensation and avoiding costly dispersion compensation designs.
(3) New multimode fibers for local area networks (LANs). As LANs and residential networks rapidly develop, a growing number of integrated wiring systems are adopting multimode fibers over digital cables, increasing the market share of multimode fibers. Multimode fibers are chosen for LANs due to the shorter transmission distances; although more expensive than single-mode fibers by 50%-100%, their compatible optical devices can use light-emitting diodes, which are cheaper than laser tubes. Multimode fibers also have a larger core size and numerical aperture, making them easier to connect and couple, and their associated connectors and couplers are less expensive. Although ITU-T has not yet accepted the 62.5/125μm multimode fiber standard due to the evolving needs of LANs, it remains widely used. In response, some companies have developed a new type of 50/125μm graded-index (G1) fiber, which differs from the traditional 50/125μm fiber in its gradient refractive index distribution, adjusting the bandwidth’s normal distribution to accommodate the use at 850 nm and 1300 nm wavelengths.
* Characteristics of Optical Cable Technology Development
(1) Selection of fiber types for specific network environments, such as backbone or metropolitan networks, dictates the overall transmission characteristics of optical cables within a broad scope, depending on specific applications and detailed standards and benchmarks.
(2) Optical cable designs must also consider the conditions of their use environment, along with the methods of construction and maintenance, to ensure a unified approach in their design.
(3) The emergence of new materials in optical cables, such as dry water-blocking materials, nanomaterials, “dry core” designs, eco-friendly cables, submarine and shallow water cables, micro cables, all-dielectric self-supporting cables, and overhead ground wires, has significantly improved cable performance.
2. Issues Worthy of Consideration in the Development of Fiber Optic Cable Technology
(1) Proactively innovate and develop new technologies with independent intellectual property rights. Since 1997, there have been 90 patents in core optical communication technologies domestically, with 9 being independently applied for. As the world’s second-largest cable producer, it should be a priority to develop technologies with independent intellectual property rights and strive to create more patents in fiber optics.
(2) Develop new products that align with advanced technological levels and are compatible with the environmental conditions and construction techniques used. The structure of optical cables depends on the environmental conditions and specific construction requirements. Moving forward, the focus of optical cable construction will continually expand with the development of access networks and residential networks. The new generation of optical cable structures and construction techniques will be based on technologies such as micro cables, blown or floating installations, and complete mini-tube or small tube systems, making full use of limited installation space. Currently, there is a lack of innovation in China, with a reliance on domestically produced optical cable products in access and residential networks.
(3) Utilize existing equipment and technology to enhance the characteristics of HYA municipal telephone cables to better serve digital services. With existing copper cables, new digital services can only be implemented based on existing characteristics. Although HYA cables can support new services like ADSL, their capacity is limited and may cause interference issues affecting previously established services as the number of ADSL connections increases. Therefore, for newly laid copper cables, it is hoped that new broadband specifications can be proposed to prepare for the launch of more new services in the future.