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Subsea Long Haul Optical Transponder


OBJECTIVE: The objective is to develop an innovative, miniaturized undersea transponder for data transmission over long haul underwater cable systems where the signal is generated from an undersea node and the use of repeaters is minimized. DESCRIPTION: New Navy concepts of operations using Autonomous Undersea Vehicles (AUV), acoustic communications, shallow water arrays, towed sensors, environmental profiling, and trip wires all require data exfiltration and fusion to be effective. Information Dominance depends on persistent accumulation and analysis of regionally captured intelligence, surveillance and reconnaissance, meteorological and oceanographic data. Current Open Architecture (OA) concepts that enable emerging undersea capabilities recognize the benefits of maximizing the utility of deployable, persistent, undersea fiber infrastructures. Recently analyzed approaches to Maritime Surveillance Systems (MSS) and other undersea operations that support using OA and standards-based bidirectional fiber optic solutions have identified the need for ocean floor node powered data transmission. The Navy needs to improve the performance and capability for AUV data exfiltration. The need to exfiltrate data collected by AUV, Unmanned Undersea Vehicles (UUV), etc from undersea nodes to shore has become a desirable capability for naval operations and scientific data collection. Approaches to undersea operations support using OA and standards-based bidirectional fiber optic solutions and have identified the need for ocean floor node generated data transmission. The current gap is in achieving the desired bidirectional data rates at increased distances. The proposed transponder, in conjunction with commercially available optical amplification with Erbium Doped Fiber Amplifiers (EDFAs) and Dense Wave Division Multiplexing (DWDM), will enable oceanographic information to be transmitted from the ocean to shore over long distances. This transponder technology will support undersea distributed networking and fusion of data from multiple sources as well as enable multi-user capability using OA infrastructure at remote seafloor nodes. Long haul undersea optical transmission systems are capable of transmitting 100 channels of 10 Gb/s optical signals over 9,000 km on a single fiber. These systems are powered from shore and typically use racks of electronics to power them. They also use repeaters to amplify signals every 40 -120 Km. (see Ref 2.) To decrease repeaters, the system generally must increase overall system end-to-end signal gain. Typical repeater-less designs seek to increase power of the optical main signal, reduce non-linear optical effects in the fiber line, improve optical fiber losses, and improve receiver sensitivity. Techniques such as suppression of stimulated Brillouin scattering (SBS), new modulation formats (Return to Zero Differential Phase Shift keying, Non-Return-To-Zero, Return-to-Zero for example), Raman amplification, and In-line Remote Pumping Amplification have emerged. (See Ref 3.) These digital modulation formats, amplification techniques, may or may not be applicable to achieve increased transmission distances at higher data rates from the seafloor than currently possible. There are many others. The goal of this topic is to determine the best combination of techniques to solve the capability gap of bidirectional data rates at distances greater than 5,000 km. Commercially available Erbium Doped Fiber Amplifiers (EDFAs), Dense Wave Division Multiplexing (DWDM), and coherent detection techniques may also apply. The undersea environment does not support cabinet size electronics and multiple repeater architectures are costly. To support deployable undersea-to-shore data transmission, this topic seeks an efficient long-haul optical transponder that is suitable for integration in an undersea network. The goal of this network is to provide power and data connectivity to various customers or tenants. It is reasonable that the components of the network itself, the hotel, will require power and bandwidth (health monitoring for example). However, a finite amount of power is available. Therefore, it is desirable for the hotel power requirement, including this transponder, to be as low as possible. For the purposes of this discussion, 5 W would be considered low and 25 W would be considered high. The transponder must demonstrate data transmission at a minimum of 1Gb/s and an objective of 10 Gb/s over a minimum of 5,000 km and an objective of 9,000km without repeating or regenerating for a minimum of 100 km and objective of 300 km with a bit-error-rate of 10-12. The proposed approach must be compatible with US and international telecom (ITU) standards, Ethernet protocols and have a 15-year, objective, 25-year goal operational life in the deep ocean. (See Ref 1.) The size of the transponder should be similar to that of a Small Form-factor Pluggable (SFP) transceiver specified by Multiple Source Agreement (MSA) group. PHASE I: The company will develop innovative concepts for a low-cost transponder the meets the requirements described above. It will identify how these technical solutions might be integrated into an underwater distributed network to achieve objective data rates, distances, power consumption, and minimal repeater use. The company will show the feasibility of developing concepts into transponders useful to the Navy and the feasibility of the solutions in meeting Navy requirements. The company will provide a Phase II development plan that establishes performance goals and key technical milestones, addresses technical risk reduction, and includes estimates of development cost and schedule as well as the associated cost, schedule, and performance risks. Reliability, maintainability, and availability will also be considered in the Phase II development plan. PHASE II: Based on the Phase II development plan, the company will develop prototype transponders for evaluation that use the innovations identified and developed in Phase I. Development will include mechanical interfaces and integration with Government underwater distributed network components. Prototypes will be tested in the laboratory to evaluate performance to Navy requirements as described above. The system will be refined and the company will prepare a Phase III development plan (including reliability, maintainability, and availability (RMA) predictions) to test and prepare the system for Navy use. PHASE III: Based on the results of Phase II and the Phase III development plan, the company will fully develop and integrate the transponder solution into an underwater distributed network node. The company will be engaged in development, testing, qualification, and certification to make the system available for Navy use. Complete system end-to-end tests will be performed on shore and at sea to demonstrate successful deployment. A manufacturing and supportability plan will be developed and will show projected production costs. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: This technology has potential commercial transition to the oil and gas industry for lowering the cost of transmission of deep ocean exploration site data, to the scientific community for enabling unprecedented ocean basin data telemetry, and to telecommunications long-haul optical transmission systems. REFERENCES: 1. Bergano, N.S."The Capabilities of Undersea Telecommunications Industry,"TE SubCom, Optical Fiber Communication Technical Conference, 2010. 2. Mortensen, R.L.; Jackson, B.L., Shapiro, S.; and Sirocky, W.F."Undersea Optically Amplified Repeater Technology, Products, and Challenges", AT & T Technical Journal, 74, Jan/Feb 1995: 1. 3. Inada Yoshihisa."Ultra-Long-Haul Repeaterless Transmission System Technologies,"NEC Technology Journal, Vol.5 (2010). Long-haul optical fiber transmission.
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