Alcatel N.v.

Alcatel

Alcatel Sel Aktiengesellschaft

Alcatel Alsthom

Gustav Veith

Rolf Heidemann

Thomas Pfeiffer

Henning Bulow

Jurgen Otterbach

A regenerator (-) for regenerating optical signals on optical transmission links (), in particular for use in a Dense Wavelength Division Multiplex (DWDM) optical transmission system. The regenerator (-) comprises optical amplification means () for compensating optical power losses, and a deterministic adaptation unit () comprising means being adapted to compensate deterministic transmission impairments of the optical transmission link (), in particular optical dispersion compensating means being adapted to compensate for chromatic dispersion of said link (). The proposed regenerator (-) further comprises a non-deterministic adaptation unit () comprising means for compensating time variant non-deterministic transmission impairments, in particular polarisation mode dispersion. In this way, the proposed regenerator overcomes transmission limitations and improves robustness of long and ultra-long-haul multi-span DWDM transmission systems with respect to deterministic and non-deterministic transmission impairments.

Optical signal regenerator and transmission system

The invention concerns a method for the amplification of wavelength division multiplex (WDM) signals in a WDM transmission system, pump light being injected into an optical waveguide of the optical transmission system contrary to the transmission direction of the WDM signals, the pump light being designed so that at least one WDM signal is individually amplified by a stimulated Brillouin scattering process in the optical waveguide produced by the pump light, as well as an optical amplifier, an optical broadband amplifier system and a WDM transmission system for it.

Method for the amplification of wavelength division multiplex (WDM) signals in a WDM transmission system, as well as optical amplifier, optical amplifier system and WDM transmission system for it

A resonator (1) for electromagnetic waves with a stabilizer can, for example, be part of a mode-coupled fiber laser. The stabilizer (2) is provided to stabilize the effective length of the resonator (1). Stabilization is accomplished in a first embodiment via two temperature controllers (3, 4) controlling the temperature of a first portion (L1) and the temperature of a second portion (L2) of the resonator (1). The temperature of the second portion (L2) is controlled as a function of an error signal generated by deviations of the resonator (1) from a nominal length. The second portion (L2) is significantly shorter than the first portion (L1).

Resonator for electromagnetic waves with a stabilizer and method for

In an optical communication system in which cable-television signals and subscriber-assigned tele-communication signals are transmitted over a passive optical network (4, 5) to at least one optical network termination (6), each optical network termination (6) requires two optical-to-electrical transducers. An optical network termination (6) is disclosed which requires only one optical-to-electrical transducer (24). The system has two transmitting devices (1, 2) which each transmit a respective optical signal (O.sub.TV, O.sub.D). In the second transmitting device (2), a second electric signal (S.sub.D), whose energy occupies a second frequency band (FB2), is processed in such a way that the energy is concentrated in a subband lying outside the first frequency band (FB1) of a first electric signal (S.sub.TV). The optical-to-electrical transducer (24) in the optical network termination (6) converts the received optical signals (O.sub.TV, O.sub.D) to an electric multiplex signal (E.sub.MUX), from which the two electric signals (S.sub.TV, S.sub.D) are recovered.

Optical communication system for cable-television signals and for

It is necessary to know the zero dispersion wavelength .lambda..sub.0, to ensure the reliable transmission of high bit-rate frequency signals via remote transmission paths. The method for determining the zero dispersion wavelength of an optical waveguide knowingly utilizes a disturbing effect that is undesirable in optical communications transmission techniques, which is able to lower the transmission quality. This effect is the so-called four-wave mixing, or in special cases a partially degenerated four-wave mixing. The method couples two light signals of different wavelengths (.lambda..sub.1, .lambda..sub.2) into an optical waveguide (4). A mixing product which occurs in the optical waveguide as a result of a partially degenerated four-wave mixing is evaluated by an analyzer (3). The wavelength of one of the two light signals is selectively varied until the optical output of the mixing product reaches a maximum. At that point the wavelength of this light signal coincides with the zero dispersion wavelength .lambda..sub.0.

Method of determining the zero dispersion wavelength of an optical

In optical transmission systems with fiber-optic amplifiers, an interruption of the fiber-optic link, e.g., due to fiber breakage, may cause a giant pulse to develop. To prevent the giant pulse from propagating in the fiber-optic link, an optical filter (7) which blocks the wavelength region of the pulse is placed in the fiber-optic link. The wavelength of the optical signal must be chosen to lie outside the wavelength region of the maximum gain of the fiber-optic amplifier.

Optical transmission system with optical filter for providing protection

A transceiver (11) for a bidirectional coherent optical transmission system with a fiber link (12) is provided with a laser (16) for transmitting a signal carrier wave, a modulator, a heterodyne or homodyne coherent detector (13), and a demodulator. To make such a transceiver (11) more economical on components, more compact in design, and less expensive to manufacture, the laser (16) is simultaneously used to transmit oscillator radiation for the heterodyne or homodyne coherent detector (13) of the same transceiver (11) and/or to optically amplify the signal carrier wave arriving from the remote transceiver (11) over the fiber link (12).

Transceiver for a bidirectional coherent optical transmission system

An optical module is used for communication over optical waveguides. To couples laser light to or from the optical waveguide (3) with as little loss as possible, the laser diode (2) must be precisely aligned with respect to the core region (22) of the end face (14) of the optical waveguide. In conventional modules, this requires costly and complicated mechanical couplers, which nevertheless do not have the necessary long-term stability. To solve the problem of how to provide a low-cost laser-to-fiber coupling which exhibits long-term stability, the optical module (1) is provided with a control facility (16, 17, 18) which controls the coupling of light on the basis of measurements of the differences in reflection factor between the core region (22) and the cladding region (23) of the end face of the optical waveguide (3). For this measurement and control, use can be made of low-priced components employed in CD players.

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Bad Liebenzell, Germany

Gustav Veith