Abstract: Signal strength in an optical fiber transmission path is attenuated in one direction to a desired lower level by incorporating a selected length of coreless, undoped fiber of the same diameter into the signal-carrying fiber. On encountering the insert, the beam diameter expands to a pre-selected value at the far end of the insert. The ratio of the beam diameter at this point to the diameter of the adjacent fiber end establishes the attenuation factor. Steps are taught for achieving high consistency in both structural strength of the attenuator as well as the attenuation factor.

Abstract: A flexible, high pressure housing is included in an equipment encloure between sections of a signal communication cable. The housing includes an axially compressed length of corrugated tubing in which the corrugations have been collapsed against the another. Housing ends are sealed to maintain a predetermined interior pressure in spite of variations in pressure outside the housing. Also included in the enclosure are structures for applying the outside pressure to the housing so that it is resiliently transversely flexible in response to similar outside and inside pressures but rigid in response to outside pressures much greater than inside pressures.