Item 



Outer Diameter, inch 



Density, Ib/ft^ 



Weight in Seawater, lb/ft 



Specific Gravity 



Breaking Strength, lb 



Recent Price per ft (1979) 



Bandwidth 



Commercially Available 

 State of the Art 



Mk 37 Wire 



0.053 ± 0.003 



99 



6.83 X 10"^ 



1.58 



20 



10 Hz/km 

 10 Hz/km 



Unarmored Optical 



Fiber (ITT or 



Sumitomo) 



0.18 ±0.002 



82 



3.27 X 10"^ 



1.32 



2-4 



$0.25-2.50 



0.5 GHz/km 

 2 GHz/km 



Ruggedized 



S-glass Optical 



Fiber 



,-4 



0.036 



108 



3.13 X 10 



1.73 



50-80** 



$0.75-1.75 



0.5 Hz/km 

 2 Hz/km 



Minimally Cabled 

 Kevlar Optical Fiber* 



0.040 ± 0.001 



127 



5.5 X 10^ 



2.03 



250 



$2.50 



0.5 Hz/km 



2 Hz/km 



This approach is clearly judged to be unfeasible because of storage volume requirements and cost 

 constraints. 



*High value is based on calculations made by means of known material properties. Low value is based on a 

 scaling of data from a 0.040-inch-OD, 32-end S-glass cable. 



Table 2. Candidate tether material characteristics. 



graded-index (GI) optical fiber from ITT was chosen as a baseline component. Previous 

 cable development work done by NOSC, Hawaii, had resulted in a "ruggedized" optical 

 fiber cable design that had an OD of 0.040 inch and a usable tensile strength of 90 lb when 

 an optical fiber proof-tested to 1% strain was used. To fabricate this cable, a 5-mil, low-loss, 

 high-strength (minimum 1% proof test) optical fiber is drawn and a protective buffer com- 

 posed of silicone RTV is dip-coated onto the fiber to produce an OD of about 12 mils. Then 

 a harder, nontacky plastic such as HYTREL is extruded onto the silicone layer until a 20- 

 mil diameter is achieved. These buffer coatings are added during the fabrication of the fiber 

 to protect it from abrasion and microbending. The glass fiber yields a "weak-link" strength 

 of approximately 2 lb in tension when proof-tested to a 1% strain or 100-kpsi load specifica- 

 tion. Developmental efforts during FY 80 determined that the buffered fiber as supplied by 

 the manufacturers had insufficient strength and stiffness for reliable deployment. To elimi- 

 nate this problem, "S-glass ruggedizing" can be used. The S-glass armored configuration is 

 made by laminating an epoxy resin and S-glass filament composite over the original HYTREL 

 jacketed fiber, increasing the OD to approximately 35 mils. The S-glass matrix is laid paral- 

 lel to the optical unit to achieve maximum strain relief and to eliminate torque while the 

 cable is under tension. The result is a usable tensile strength of approximately 60 pounds 

 (using 1% proof-tested fiber) and a degree of built-in stiffness that tends to prevent cable 

 breakage at the peel-off point on the inner layer. Figure 5 shows the cable cross section. 



17 



