Such a device, installed on the bulkhead of the communications bottle of the NOSC 

 free swimmer, transfers optical information conveyed by the deployable fiber-optic tether 

 cable to and from the optoelectronics in the vehicle in a robust and rehable manner. The 

 connector on the cable can be demounted in a matter of seconds, allowing rapid replacement 

 of the tether cable spools. This is a valuable feature for practical, at-sea operation of the 

 system. In the event of cable breakage or operator error in installing the connector into the 

 penetrator, there is no danger of water leakage because the penetrator itself provides the 

 pressure integrity function. 



4.0 CONCLUSIONS AND RECOMMENDATIONS 



4.1 PROGRESS TO DATE 



A fiber-optics communication link for EAVE WEST has been demonstrated in the 

 following areas: 



1 . A deployed optical fiber cable was payed out underwater from a hand-wound coil 

 mounted on the EAVE WEST free-swimming submersible in 1979 (ref 4). It was 

 demonstrated that both armored and ruggedized optical fibers could be deployed 

 successfully from a free-swimming submersible with little penalty in speed, per- 

 formance, or power consumption. The tether cable diameters ranged from 0.020 



to 0.036 inch, and included both ruggedized and unstrengthened optical fiber units. 



2. With knowledge gained from this test of hand-wound fiber canisters, computer- 

 controlled machinery has been constructed for the automatic precision fabrica- 

 tion of long, pretwisted deployment spools at low cost. We are now capable of 

 producing high-capacity, precision-wound spools of expendable optical tether 

 cable in packages suitable for deployment from small undersea vehicles with 

 negligible drag penalty. To date, cable lengths as great as 4 km have been payed 

 out underwater at speeds up to 100 fps. 



3. Undersea vehicles need considerable standoff range if they are to be practical 

 for pipeline inspection applications (see appendix). Work was performed in 

 1978 to demonstrate an optimized fiber-optic coding system, PFM, which 

 allows the ultimate in standoff range to be obtained with any optical fiber 

 transmission line (ref 6 and 7). For use in conjunction with the sync- 

 interleaved data multiplexer, an optimum television/command control data 

 interface has been designed, fabricated, tested, and demonstrated in the 

 laboratory. 



4. We are presently experimenting with cabhng techniques to ruggedize two ultra- 

 low attenuation optical fibers, each more than 5 km in length, from Sumitomo 

 of Japan. Using fibers of this quality (0.68 dB/km) in conjunction with the 

 PFM electronics operating at 1.57 ^lm wavelength, a 25— 50-nmi repeaterless 

 standoff range might be obtained. 



5. Work has been progressing on a number of ancillary fiber-optic components 

 for use in the ocean. A most important device is the high-pressure penetrator. 

 It would be quite difficult to build a practical undersea system without such 



a device. We have operated our devices to pressures well in excess of 10 000 psi 

 with no failures, and have surpassed the MIL temperature range of-40°C to 

 -l-80°C. These devices permit both at-sea demounting of the optical cable from 



37 



