RT&L FOCUS AREA(S): Directed energy TECHNOLOGY AREA(S): Battlespace Environments OBJECTIVE: Develop a compact electro optic efficient, 2-band efficient, pico second mj energy per pulse scalable blue (450 nm)-green (550 nm) laser transmitter/receiver that can be used for underwater optical communications with optical link > 100m and data rate > 1 Gb/s. DESCRIPTION: Underwater optical wireless communication with long optical link and high data rate is in great demand by the Navy due to the increased information transfer between submarines, unmanned vehicles and devices deployed underwater. Although tremendous progress has been made in the field of acoustic wireless lines, due to the attenuation of acoustic waves in water and the bandwidth of acoustic communication (10 kb/s), it is still far below the requirement of current applications. Radio Frequency (RF) communication has improved bandwidth but the link distance is generally < 10 m and limited by the very short penetration depth of RF signal in the water. Optical wireless communication with sufficient bandwidth, high security, and low time latency is believed to be the most promising approach to realize reliable long-distance and high-speed underwater communication links. Optical wireless communications with Gb/s bandwidth have been demonstrated by light in the blue (450 nm)-green (550 nm) spectrum. However, the optical links cannot meet the requirement of the Navy's applications due to low output power of the compact laser transmitters currently available and the large attenuation of sea water even in the blue-green spectrum region. Therefore, compact, high electro optic efficient powerful pulse laser transmitters at the low attenuation wavelength are in high demand for underwater communication with optical links > 100 m. The pulse laser transmitter shall operate in advance pulse code modulation technique to preserve the electrical power and able to increase the pulse energy and peak power that may require to transmit data at required distance. In this STTR topic the proposer and/or academia should develop the system architecture, modeling, management, documents and implementation of the design based on Open Model Based Engineering Environment (MBEE). This STTR topic will increase mission capability by enhancing underwater communication links and increasing communication data rate and bandwidth, while providing secure and stealthy communication. This topic looks for a prototype with the following parameters: Wavelength: Wavelengths that transmit through the sea water with low attenuation Average Power Output: Threshold: 10 W; Objective: 50 W Pulse width: pico second (ps), threshold < 5 ps; Objective < 1 ps Pulse energy >1 mJ per pulse Pulse Repetition rate ~ kHz Bandwidth: Threshold: 1 Gb/s; Objective: 5 Gb/s Achievable link distance: Threshold: 100 m; Objective: 200 m Beam Quality (M2): Threshold: 1.5, Objective <1.1 Weight: Threshold: 2 lbs, Objective 1 lb Volume: Threshold: 4 inch3, Objective <2 inch3 PHASE I: Design and analyze a concept of compact electro optic efficient pico second pulse laser transmitter and detector for laser receiver with > mJ per pulse per band architecture for underwater optical communication with optical link > 100 m and data rate > 1 Gb/s. The pulse laser receiver shall be able to decode the information from pulse code transmitter. Provide compact innovative efficient approach of transmission of optical information based on advanced pulse code modulation and detection. Demonstrate the feasibility of the concept with a power-scalable laser transmitter at a wavelength for underwater wireless communication in a bench top experiment. The Phase I Option, if exercised, will provide the prototype design and provide the specifications to meeting Phase II goals. Use the Open Model Based Engineering Environment (MBEE) method to develop a solution like modeling, design and document generation. PHASE II: Develop and deliver a prototype of a 2-band blue/green laser system based on the concept developed in Phase I and the Phase II Statement of Work (SOW). Optimize the design and development of the Phase I laser concept to prototype a portable laser transmitter capable of producing up to 10 W output power > 1 mJ per pulse. Deliver the optical transmitter and detector system for evaluation at a Navy lab. If a Phase II Option is exercised, work with the Navy to test and evaluate the initial prototype product (hardware and software) at a Navy facility. If the Phase II Option II is exercised, perform further test and evaluation at a Navy facility and modification if necessary to meet the performance benchmarks before the fieldable prototype product (hardware and software) shall be delivered to the Navy. PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning optical transmitting/detection system to Navy submarine platforms. Assist in the development and transition of the laser transmitter/detector for underwater optical communications. This technology is applicable on other DoD platforms and commercial applications such as environmental monitoring, offshore exploration, and disaster precaution. REFERENCES: Zeng, Z.; Fu, S.; Zhang, H.; Dong, Y. and Cheng, J. A survey of underwater optical wireless communications. IEEE Communications Surveys and Tutorials, Vol. 19, 2017, pp. 204-237. https://ieeexplore.ieee.org/document/7593257/authors#authors Johnson, L.J.; Green, R.J. and Leeson, M.S. Underwater optical wireless communications: depth dependent variations in attenuation. Applied Optics, Vol. 52, 2013, pp. 7867-7873. https://doi.org/10.1364/AO.52.007867 Johnson, L.J.; Jasman, F.; Green, R.J. and Leeson, M.S. Recent advances in underwater optical wireless communications. Underwater Technology, Vol. 32, 2014, pp. 167-175. https://www.researchgate.net/publication/268033954_Recent_advances_in_underwater_optical_wireless_communications Tian, P.; Liu, X.; Yi, S.; Huang, X.; Zhang, S.; Zhou, X.; Hu, L.; Zheng, L. and Liu, R. High-speed underwater optical wireless communication using a blue GaN-based micro-LED. Optics Express, Vol. 25, 2017, pp. 1193-1201. https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-2-1193 Chen, Y.; Kong, M.; Ali, T.; Wang, J.; Sarwar, R.; Han, J.; Guo, C.; Su, B.; Deng, N. and Xu, J. 26 m/5.5 Gbps air-water optical wireless communication based on an OFDM-modulated 520-nm laser diode. Optics Express, Vol. 25, 2017, pp. 14760-14765. https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-13-14760
