Abstract: A noise limiter for a binary circuit in which a thin film superconductor is put in shunt between a transmission line and ground. The thin film exhibits a gradual transition region as a function of current between normal conduction and the completely superconductive state. The dimensions of the thin film are chosen such that a high level signal on the transmission line falls in the gradual transition region and the impedance of the shunt is greater than the characteristic impedance of the transmission line while a noise component on the low level signal falls in the superconductive region and therefore is reflected by the zero-impedance shunt.

Abstract: Filter arrangements (400,500,600) are disclosed for tunable channel selection in optical wavelength division multiplexed systems. Each filter arrangement has an etalon device (e.g. 401-403) as a simple, compact, in-line component which is rotatably adapted for interposing between the ends of fiber optic cables for interconnecting the cables. An optical beam emanating from a free end of each cable end is focused and directed to the etalon device by a collimated lensed connector (e.g. 411). Identical etalon devices may be stacked and ganged for rotation in unison to increase the number of system channels that may be propagated. Non-identical etalon devices may be stacked and made independently rotatable to increase the free spectral range of the system.

Abstract: An articulating waveguide arm assembly, comprising long arm segments, (11, 12, 15, 17, 19) and short corner segments (13, 14, 16, 18) has a single-mode hollow dielectric waveguide located inside each segment and an optically reflecting device (33, 34, 37, 38, 39) located at the end of each segment. The waveguide assembly is mechanically affixed to a robot assembly having protruding side shields (65, 66). The robot assembly includes a pair of long arms (61, 62) corresponding to a pair of the waveguide arms (15, 17). Another waveguide arm segment (12) of the waveguide assembly passes over the protruding side shields and terminates in a pair of successive corner segments (13, 14) for enabling a laser beam propagating through this long arm segment to enter into one of the pair of long waveguide segments (61).

Abstract: Single longitudinal mode operation is achieved and maintained under CW and high speed (Gbps) current modulation conditions by a short coupled cavity laser including a short cavity semiconductor laser having two parallel mirror facets and a reflective surface spaced apart from and in predetermined relationship with one of the mirror facets. A short external cavity resonator is formed between the one mirror facet and the reflective surface. In general, the laser cavity length is related to the external cavity resonator length by the equation, nL=md, where nL is the effective optical length of the injection laser, d is the length of the external cavity resonator, and m is a positive number preferably between 2 and 10.

Abstract: An optical pulse equalization technique for minimizing pulse dispersion in a single-mode fiber transmission system where there is a mismatch between the optical source (1) wavelength and the wavelength at which a transmission single-mode fiber (2) has a zero total dispersion utilizes the positive and negative dispersion characteristics of single-mode fibers on both sides of the zero total dispersion wavelength. A second equalizer single-mode fiber (3) is used as an optical equalizer. This equalizer single-mode fiber has the property that the optical source wavelength lies at a value which is between the zero dispersion wavelengths of the transmission and equalizer single-mode fibers. The transmission fiber and the equalizer fiber have different dispersion signs at the source wavelength and the length of the equalizer fiber is chosen to be equal to the length of transmission fiber times the ratio of the dispersions for the fibers at the source wavelength.

Abstract: A tunable radiation source employing the stimulated Raman-scattering process is disclosed. The source generates several orders of Stokes radiation in an optical-fiber oscillator cavity, which Stokes radiation may be independently tuned by incorporating separate tuning elements for the several Stokes orders. Several different arrangements of fiber and tuning elements are disclosed.

Abstract: The optically pumped submillimeter wave lasers employing molecular gases having dipole moments are improved by employing as a polyatomic buffer gas a molecular gas or vapor of a hydrocarbon having a significantly large vibrational heat capacity in relation to its molecular weight. An example is C.sub.6 H.sub.14 added to such lasers as the methyl fluoride laser at 496 micrometers. Other examples of saturated hydrocarbon buffers are also given; and in each case the vapor molecule is complex enough to absorb many vibrational quanta from the active molecules, yet is small enough to move rapidly to the tube walls.

Abstract: There is disclosed a time-dispersion tuned Raman oscillator which makes use of the frequency-dependent transit time of Stokes radiation through a long optical fiber. Time-dispersion tuning is effected by synchronizing Stokes radiation of the desired frequency with a pump pulse. This synchronization may be accomplished either by adjusting the delay of the feedback pulse relative to a pump pulse or by adjusting the repetition rate of the pulsed pump laser.