At&t Bell Laboratories

Other

At+t Corp.

Craig D Poole

Herman M Presby

Jack Harriman Winters

Zygmunt Haas

Mario A Santoro

A battery or solar-powered apparatus for measuring and displaying optical power transmitted through an optical fiber. The apparatus has a measuring circuit comprising an optical detector (602), a current/voltage converter (704) and a control circuit (702) which provides timing signals and controls the power applied to the measuring circuit. The apparatus is secured within a housing (102) and is sufficiently small and light such that permanent, in-line attachment to the optical fiber is possible. In a first embodiment, a voltage proportional to the measured optical power is available at an output jack (214) attached to the housing (102). The jack further comprises a switch (1760) which enables power to the apparatus during a measurement period. An alternative embodiment comprises an analog/digital converter (1202) which provides a digital representation of the measured optical power. Low-power displays, such as liquid crystal displays (112, 312), provide direct visual output of the digitized representation of the measured optical power, selectably in units of dBm/dB.

Optical power meter using low-power measurement circuit

Efficient conversion between the LP.sub.01 and the LP.sub.11 modes in a two-mode optical fiber is realized in a fiber grating fabricated by forming a series of longitudinally-spaced cuts in the fiber cladding, and then annealing the fiber in the region of the cuts. The latter step uses the surface tension of the molten glass to transform the corrugation on the cladding into a sinusoidal deformation of the fiber core.

Optical fiber spatial mode converter using periodic core deformation

It has been discovered that improved performance and reduced size can be realized in dual-mode fiber dispersion compensators by careful alignment of the mode pattern relative to the plane of the bend of the spooled fiber. In particular, minimum loss occurs when the null line of the LP.sub.11 mode lies in the plane of the bend. Arrangements for insuring that the fiber assumes the correct orientation for minimum bending loss are disclosed.

Low-loss dual-mode optical fiber compensators

The polarization-dependent distortion of an optical signal transmitted through an optical fiber is reduced by aligning the polarization of the optical signal to minimize the received signal distortion. A polarization controller (a device which can change the polarization of light in an optical fiber) may be located at either the input or output end of a long haul optical fiber system and is used to align the polarization of the signal to minimize the received signal distortion. Automatic operation of the polarization controller can be obtained by using a steepest-descent method based on a distortion measure of the received signal for the optical signal transmitted through the optical fiber to generate control signals which are used to control the polarization controller.

Fiber-optic transmission polarization-dependent distortion compensation

An optical fiber communication system according to the invention comprises, in addition to conventional single mode (SM) optical fiber, dispersion compensating (DC) optical fiber. The DC fiber is selected such that its chromatic dispersion (D.sub.DC (.lambda.)) and first derivative of the chromatic dispersion with respect to wavelength (D'.sub.DC (.lambda.)) at a wavelength .lambda.=.lambda..sub.op have opposite sign from those of the SM fiber. Advantageously, the DC fiber is selected such that L.sub.DC .multidot.D.sub.DC (.lambda.)+L.multidot.D(.lambda.) is approximately zero at .lambda.=.lambda..sub.op, and such that D'.sub.DC (.lambda.) is approximately equal to --(L/L.sub.DC).multidot.D'(.lambda.) at .lambda.=.lambda..sub.op, where L.sub.DC and L are appropriate lengths of DC and SM fiber, respectively. Typically, L is much greater than L.sub.DC, and .lambda..sub.op typically is about 1.5 .mu.m, e.g., about 1.56 .mu.m. Preferred embodiments of the invention have low chromatic dispersion over a substantial wavelength region (e.g., dispersion less than 1.5 ps/nm.multidot.km over at least 50 nm) that includes .lambda..sub.o, facilitating wavelength division multiplexing.

Chromatic dispersion compensated optical fiber communication system

Chromatic dispersion is efficiently compensated in a compact device by combining a spatial mode converter with a dispersive waveguide having a dispersion characteristic of substantially equivalent magnitude, and opposite sign, to the desired amount of dispersion to be compensated. The spatial mode converter exchange the optical energy from one propagating spatial mode to another spatial mode whose propagation is supported by the multimode or dual-mode fiber. This apparatus is applicable to lightwave repeaters, regenerators, transmitters, and receivers.

Apparatus for compensating chromatic dispersion in optical fibers

A mode coupler is disclosed which utilizes a circularly symmetric perturbation in an electromagnetic waveguide. Due to the circular symmetry of the perturbation, exact cross-sectional alignment of the perturbations is not needed when several of the devices are cascaded. Further, the mode coupling response is wavelength dependent, and therefore, may be employed in electromagnetic filtering applications.

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Ocean, NJ, United States of America

Craig D Poole