METHOD AS A PRE-CONDITION FOR A GAIN CONTROL, OPTICAL ACCESS NETWORK, CENTRAL STATION AND TERMINAL

Abstract

The invention concerns a method as a pre-condition for a gain control of an optical amplifier that amplifies a whole signal out of a multiple of optical signals and where each of these signals includes regular gaps, in which these optical signals are synchronized with respect to each other such that the gaps coincide, as well as a tree-shaped optical access network, a central station, and a terminal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described with the aid of the accompanying drawings:

FIG. 1 shows a tree-shaped optical access network according to the invention and above it the behavior with and without the method according to the invention.

On the basis of FIG. 1 this invention now will be described.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows at the bottom a tree-shaped optical access network with a central station CS, an optical amplifier OA, a multiplexer MX for combining the signals with different wavelengths, a couple of power splitters PS, and a multiple of subscriber units or terminals, one of these being denoted as SUx.

First the known operation of such network will be described:

Each power splitter PS together with the subscriber units SUx connected thereto builds one group working with one and the same operating wavelength. Insofar we only regard the upstream direction from the subscriber units to the central station. Each such group works with a wavelength different from the wavelengths of the other groups. Within one group the subscriber units' operation is regulated by a scheduler being part of the central station. Each scheduler grants time slots to the different subscriber units assigned to it, such that on the one hand there is no overlap and on the other hand no unnecessary gap on either of the wavelengths.

In order to cope with the already mentioned situation of inserting a new subscriber unit to the access network or restoring the network after an interruption it is necessary to reserve a certain gap where a subscriber unit may try to register without disturbing the others.

Between the central station CS and the multiplexer MX we thus have the situation illustrated at the top of FIG. 1 with the double arrows representing those gaps.

As the schedulers are working independent from one another, the gaps are arbitrary with respect to one another.

Here the invention suggests to align those gaps as illustrated in the middle of figure 1, creating a time interval where all wavelengths are silent.

This can easily be achieved by a cooperation of the different schedulers. Such cooperation can be restricted to the alignment of the delays on the respective access line in order to ensure the gap being located at the foreseen time period. The measuring and the taking into account of delays for other reasons anyway are being done.

When such network does not have centralized schedulers or the like, but works on a decentralized basis, than the terminals are to ensure the common silent period. This for example can be done by adjusting the gaps at the position of the optical amplifier to prescribed points in time. Here too the delays have to be taken into account.

By this measure the anyway necessary transmission free time interval is the basis of a situation free of cross gain effects and with zero signal dynamics.

Claims

1. A method as a pre-condition for a gain control of an optical amplifier that amplifies a whole signal out of a multiple of optical signals and where each of these signals includes regular gaps, wherein these optical signals are synchronized with respect to each other such that the gaps coincide.

2. A tree-shaped optical access network with a central station and at least one optical access line connected thereto for a whole signal out of a multiple of optical signals destined for incoming at the central station, where each of these signals includes regular gaps and comes from different terminals and with a repeater looped into the optical access line and including an optical amplifier for the whole signal, wherein the central station is build such that it grants the terminals for sending and that such grants occur such that the gaps of all signals coincide on the optical access line.

3. A central station for a tree-shaped optical access network with a central station and at least one optical access line connected thereto for a whole signal out of a multiple of optical signals destined for incoming at the central station, where each of these signals includes regular gaps and comes from different terminals and with a repeater looped into the optical access line and including an optical amplifier for the whole signal, wherein the central station is build such that it grants the terminals for sending and that such grants occur such that the gaps of all signals coincide on the optical access line.

4. A terminal for a tree-shaped optical access network with a central station and at least one optical access line connected thereto for a whole signal out of a multiple of optical signals destined for incoming at the central station, where each of these signals includes regular gaps and comes from different terminals and with a repeater looped into the optical access line and including an optical amplifier for the whole signal, wherein the terminal is build such that it observes in its emission silent periods such that at the optical amplifier the silent periods occur at given times.

5. The tree-shaped optical access network according to claim 2, characterized in that the central station is build such that it grants the terminals for sending and that such grants occur such that the gaps of all signals coincide on the optical access line.

6. The tree-shaped optical access network according to claim 2, characterized in that the terminals are build such that they observe in their emissions silent periods such that at the optical amplifier the silent periods of all terminals coincide.