Alcatel N.v.

Other

Alcatel

Itt Industries, Inc.

International Standard Electric Corporation

Standard Elektrik Lorenz Ag

Manfred Kaiser

Rolf Heidemann

Thomas Pfeiffer

Friedemann Mohr

Horst Ohnsorge

J&uuml;rgen Anhorn

Klaus Herse

Frank Hehl

Kate Hiepe-Wohlleben

Wolfgang Stiepek

Rainer Hausser

Dieter Kuppers

An optical switching unit is disclosed which permits switching from faulty components to standby components in optical transmission systems. A component in this connection may be a transmit laser or an optical fiber, for example. The optical switching unit (OSE) according to the invention contains an n&times;m optical space switch (ORS) whose ports (P A . . . PNA; P B . . . PMB) are monitored by photodiodes (M A, M B). The photodiodes provide a control unit (SE) with information as to whether and, if so, what signals are arriving at the ports. The control unit (SE) controls the position of the optical switch (ORS) in accordance with program instructions. The switching unit controls itself, i.e., incorporation of a higher-level control center is not necessary. It thus allows very short switching times and has many applications; it is particularly suitable for use in modular optical transmission systems.

Optical switching unit, particularly for switching to standby components in optical transmission systems

Known optical amplifiers, which are used in a light transmission path to amplify the light signals to be transmitted, have the disadvantage that the semiconductor lasers, used as pump lasers therein, are very sensitive to feedback. According to the invention, the operating current of such pump lasers (4) is modulated at a high frequency, which causes the pump laser to operate in a multi-mode, thereby making it insensitive to feedback. For example, the operating current is DC, on which AC is superimposed. In the event the optical amplifier has two pump lasers, their operating current is also modulated. Both pump lasers are then advantageously alternately switched on and off at a sufficiently high switching frequency, which also prevents reciprocal interference.

Optical amplifier

There is no problem to excite the fundamental mode in a single-mode optical waveguide, if a laser is used whose operating wavelength is above the cutoff wavelength of the guide. However, these lasers are presently very expensive. Especially for the use in the subscriber area, where the relatively short transmission lengths allow to accept a certain amount of attenuation, it is proposed to use an inexpensive laser (6) whose operating wavelength, however, lies below the cutoff wavelength of the coupled optical waveguide (10). The excitation of only the fundamental mode is, according to the invention, possible with such a laser (6). A single-piece metallic module housing (1) is provided in which the laser (6), being moved perpendicularly to the module housing axis (1), is aligned to it by adjusting screws (12). A magnifying optic (9) is provided. The magnification causes a decrease of the angle at which the laser light reaches the face of the optical waveguide (10). The optical waveguide (10), being coaxially centered in a cylindrical bore (5), is adjusted axially to an optimal coupling and then fixed.

Laser module

For short-distance communication systems, particularly for optical-waveguide links in the subscriber area, it is proposed to operate the standard single-mode optical waveguide for long-distance applications, which is optimized for the wavelength range from 1300 nm to 1600 nm, with optical transmitters and optical receivers whose operating wavelengths lie clearly below the cutoff wavelength of the optical waveguide. By means of a suitable stable laser-waveguide coupling, it is ensured that single-mode operation is achieved, which is necessary to transmit digital signals at high bit rates. The increased loss of the optical waveguide at 800 nm can be accepted because of the relatively short length of subscriber lines. Both unidirectional and bidirectional transmission over a single optical waveguide using wavelength-division or modal multiplexing is possible.

Broadband optical communication system, particularly in the subscriber

The multiplexer/demultiplexer consists of a plurality of elements (105, 106, 107, 108) made of optically transparent material which are cemented together and on which filter layers (101, 102, 103, 104) are deposited so as to form wavelength-selective beam splitters.

Optical multiplexer/demultiplexer

The variable optical attenuator (1) comprises two spherical lenses (7, 8), one at the input end and one at the output end, between which a bundle of parallel rays is present. A disk (4) having areas (9) with neutral density filters (10) of different attenuation is rotatable through the bundle of rays. A locking mechanism (13, 14, 15) acts on a stub shaft (11) at the disk (4), and its stop positions correspond to the locations of the areas (9). This permits the attenuation of the attenuator (1) to be adjusted in steps.

Variable optical attenuator

A fiber optic connector is disclosed capable of joining in proper alignment the uncentered ends of two optical fibers mounted in ferrules. Each ferrule is rotatably supported inside an eccentric bore of a connector sleeve by means of a rotatable cage whose balls or rollers have different diameters. The two cylindrical connector sleeves are capable of being mated in a connector receptacle with the optical fibers therein adjusted to exact lateral alignment.

Growing community of inventors

Hemmingen, Germany

Manfred Kaiser