Ultra-Low-Loss Fibers Enable Advanced Performance in Submarine Applications By Dr. Merrion Edwards and Rita Rukosueva
The submarine market space consists of two main segments: repeatered and unrepeatered networks. Repeatered networks require in-line amplification and can be anything from regional networks of up to 3,000 km, or intra-continental networks of up to 6,500 km, to trans-oceanic networks which can extend to 13,000 km.
is another critical element. Since, these networks vary greatly in number of channels (up to 96) and in length (from about 400 km to 13,000 km) several fiber types were developed and are being used to achieve those capacities per fiber and transmission distances in the most cost-efficient way.
In contrast, unrepeatered submarine systems are short-haul undersea networks designed for distances of up to around 400 km that are achieved without in-line amplification.
For regional systems up to 3,000 km a standard negative dispersion submarine fiber with a low positive dispersion slope (-D, S>0) such as Corning® Vascade® LS+ fiber, is used in the transmission span, or if more power handling capability is required a large effective area, negative dispersion (-D, S>0) submarine fiber like Corning® Vascade® LEAF® fiber is deployed, as shown in Figure 1. For inter-continental systems that extend beyond 3000 km and up to 6500 km, the system often needs to cope with higher transmission powers but also needs a low dispersion slope and so a hybrid combination of a high power handling negative dispersion large effective area submarine grade fiber (like Corning Vascade LEAF) and a standard negative dispersion fiber (like Corning Vascade LS+) with a low dispersion slope is often used within each transmission span. Dispersion compensation is achieved in regional and inter-continental networks by inserting a span (or part of a span) of positive dispersion fiber, such as standard singlemode fiber or a low-loss fiber.
This range in network types and lengths means that submarine networks have a variety of reach and capacity needs, and as a consequence have diverse requirements in terms of telecommunications systems and optical fiber solutions. Common to all networks however, is the need to minimize the signal loss due to fiber attenuation. Lowering the fiber attenuation yields cost efficiencies, and as a consequence ultralow-loss fibers bring significant benefits to all submarine networks. Submarine Network Design Needs a Diverse Fiber Portfolio Repeatered submarine networks use amplification to overcome fiber attenuation as so low-loss fibers can enable significant savings in amplification costs. However, repeatered networks are also limited by the accumulation of chromatic dispersion over the transmission path that degrades the signal. For such networks, effective management of and compensation for dispersion
Ultra long-haul systems are over 6,500 km, and in these systems, the dispersion slope of the fiber becomes a problem as it results in different
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