Showing papers presented at "Optical Fiber Communication Conference in 1981"

Semiconductor laser noise in an interferometer system

Abstract: The noise of semiconductor laser light after passing a Michelson interferometer has been measured for gain guided as well as index guided double-heterostructure injection lasers. This noise is mainly due to the partition noise and the frequency noise of the laser emission. Unless the interferometer is perfectly balanced, the observed noise is several orders of magnitude larger than the usual intensity noise of semiconductor lasers.

Heterodyne-type optical fiber communications

Abstract: Standard optical fiber communication systems employ intensity-modulation/direct-detection schemes. This is noise-carrier communication and in a sense is more primitive than the radio engineering in Marconi’s age. However, it has the practical advantage of system simplicity and low cost. On the other hand, some applications of optical fiber communication exist in which a long repeater separation is the primary concern; an example is submarine optical cable communication between islands, in this case, the improvement of the bit-error rate (BER) by a coherent modulation/demodulation scheme such as PCM-PSK or PCM-FSK may be advantageous even at the sacrifice of simplicity and low cost.

Current sensor using state-of-the-art fiber-optic interferometric techniques

Abstract: Over the past five years, the detailed analysis of the phenomena associated with interferometric measurements in a guiding medium has yielded a stability and sensitivity improvement of over 3 orders of magnitude. The most spectacular progress derived from the long forgotten virtue of the Sagnac (closed path two-wave interferometer) configuration: reciprocity. These concepts have found popular application in the fiber-optic gyroscope.1 We have applied them to a novel device, a current sensor utilizing the Faraday effect in a dosed loop guiding interferometer.

Low-loss LiNbO_3 waveguide bends with coherent coupling

Abstract: Low bending losses have been achieved in single-mode Ti:LiNbO(3) channel waveguides by utilizing coherent coupling effects between closely spaced abrupt bends. A variety of multiple-bend structures has been evaluated. Losses as low as 0.08 dB per coupled 1 degrees abrupt bend have been measured, as compared with 0.8 dB per isolated 1 degrees abrupt bend.

Statistics of backscattering in single-mode fiber

Abstract: Rayleigh backscattering in single-mode fibers is helpful in loss measurements by OTDR and OFDR but troublesome when causing feedback to a semiconductor laser or when interfering with the signal in interferometric sensors. We show that the backscattered fraction of power Q = Iscatt/Iinput may fluctuate strongly for even minute variations of optical frequency ω or ambient temperature T, pressure p, or strain e, possibly imposing severe limitations on applications.

Experimental integrated-optic circuit losses and fiber pigtailing of chips

Abstract: Experimental integrated optic circuit losses, including waveguide bend, waveguide offsets, metal electrodes, and fiber-to-channel coupling, are presented. Coupling measurements from single-mode fibers to straight waveguides show losses less than 1 dB. Integrated optic circuit losses due to waveguide bends and offsets were calculated and measured; these data are in excellent agreement. A four-section \Delta\beta reversal switch has been permanently coupled to single-mode fiber pigtails with coupling losses approaching the measured optimum and theoretically predicted value.

Reduction of hydroxyl contamination in optical fiber preforms

Abstract: Hydroxyl ion contamination of optical fiber cores, and to a lesser extent cladding, proves a serious impediment to low loss, especially at longer wavelength (1.3-1.6 μm). In MCVD this contamination originates primarily from hydrogenic impurities in the gas supply, reactants, or leaks in the deposition apparatus. The level of contamination produced by this impurity is controlled by the reaction.

Fiber Fabry-Perot interferometers

Abstract: A Fabry-Perot (FP) interferometer or etalon is an optical device that can detect, in a digital way, temperature, pressure, or mechanical vibration via the change in optical path length between two surfaces with high reflectivity. In this paper we report some studies of a fiber Fabry-Perot etalon (FFPE). Unlike a conventional FPE consisting of bulky structures, FFPE does not require exact parallelism between two reflection surfaces. It is small, flexible, and can be very long, yielding high measurement sensitivity. Single-mode, multimode, and Selfoc fibers have been studied.

Aspects of optical frequency-domain reflectometry

Abstract: Optical time-domain reflectometry (OTDR) has proved to be a useful tool for fiber and fault diagnostics1 in the laboratory and in operating systems. This work is a preliminary analytical and experimental investigation of optical frequency-domain reflectometry (OFDR), applying swept frequency rather than pulse techniques.

Optical frequency-domain reflectometry in single-mode fibers

Abstract: The spatial distribution of attenuation and birefringence along a single-mode fiber can be determined by measuring from one fiber end the dependence of the Rayleigh backscatter amplitude on optical (spatial) frequency. A Fourier transform is necessary for conversion to the space domain. This is the principle of optical frequency domain reflectometry (OFDR).