REGION OF THRESHOLD EXTENSION 



Figure 16. Receiver operating characteristics compared with theoretical predictions. 



required to implement optical links on a variety of undersea platforms and devices. The 

 penetrator provides the means by which the optical signals carried by the fiber are transferred 

 between the high-hydrostatic-pressure environment of the cable and the low-pressure environ- 

 ment of the electronics package or manned portion of any underwater system. Thus it is 

 a key component required in practically all proposed underwater fiber-optic applications. 



An optimum fiber-optic penetrator design would incorporate the many features that 

 have evolved over a long period and are now available in present-day electrical penetrators. 

 Unless these proven features are fully utilized, undesirable effects could negate the advantages 

 that fiber-optic cables have in comparison with coaxial cables. The following specific design 

 recommendations should be incorporated. 



1 . The penetrator design should exhibit low optical throughput attenuation. 

 Insertion-loss characteristics should be comparable to and at least as 

 repeatable as the better optical fiber connectors presently available in the 

 marketplace. The optical characteristics should be maintained over the 

 entire spectral region used for communications. 



2. The penetrator design should lend itself to efficient certification procedures. 

 It should be possible to test and certify the pressure-integrity function of the 



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