US 5,982,791 A · Wavelength tracking in adjustable optical systems

Abstract

An optical system such as an add and/or drop WDM multiplexer allows the wavelength fluctuation of an optical carrier to be tracked so that a corresponding fiber Bragg grating (FBG) can be responsively tuned. The preferred embodiment of the wavelength tracking system in an optical system such as an add and/or drop module includes a three-port optical circulator, three optical fibers, a series of tunable FBGs, a source of a broadband optical noise signal, an optical spectrum analyzer (OSA), and an FBG tuner. In operation, an LED generates modulated probe lightwaves that are inserted into a drop module. The LED lightwaves and the optical carriers propagating through the drop module are monitored by an OSA. The monitoring procedure determines the conditions, in terms of target wavelengths of the FBGs, and the stability or instability of the optical carriers. The FBGs are then tuned in response to the FBG and optical carrier information. In another embodiment, the wavelength of an optical carrier is tracked using a modulated tracking grating and an FBG is adjusted in response to the tracking information.

Claims18

Dependent claims

A wavelength tracking and adjustment system comprising:

an optical path having an input connected to receive an optical carrier having a nominal wavelength;
a tunable grating formed along said optical path, where said tunable grating is adjustable to selectively reflect substantially all of said optical carrier having said nominal wavelength;
means for monitoring a reflectivity characteristic of said optical path in real time, said means for monitoring including a modulated broadband optical signal generator optically connected to said optical path for inserting a modulated broadband optical signal into said optical path in combination with said optical carrier, and further including an optical spectrum analyzer optically connected to said optical path for monitoring said optical carrier and reflectivity of said tunable grating, said reflectivity of said optical path being representative of a real-time reflected wavelength of said modulated broadband optical signal;
means, responsive to said means for monitoring, for dynamically adjusting said tunable grating in order to compensate for fluctuations in wavelength of said optical carrier relative to said nominal wavelength.

1 more element

A dynamically adjustable optical system comprising:

a first directional optical transfer device having first, second and third ports;
a first waveguide connected to said first port of said first directional optical transfer device;
a second waveguide connected to said second port of said directional optical transfer device;
a first tunable grating located along said second waveguide for reflecting optical energy;
means, in optical communication with said first directional optical transfer device, for tracking a wavelength of an input optical carrier, said means for tracking including:
means for introducing a modulated broadband optical signal into said second waveguide;
and
means for monitoring said modulated broadband optical signal after said signal has interacted with said first tunable grating in order to determine a wavelength band of reflectivity of said first tunable grating;
means for tuning said first tunable grating to reflect said input optical carrier back to said first directional optical transfer device, said means for tuning being responsive to said means for tracking said wavelength of said input optical carrier;
and
a third waveguide connected to said third port of said first directional optical transfer device for propagating said input optical carrier, said first, second and third ports of said first directional optical transfer device being configured such that said third waveguide is one of a source of said input optical carrier and a receiver of said input optical carrier.

8 more elements

A method of transmitting an optical carrier comprising the steps of:

providing a first directional optical transfer device having at least three optical ports for the input and output of optical carriers;
providing at least three optical transmission paths having a one-to-one correspondence with said optical ports;
optically coupling at least one tunable grating to one of said at least three optical transmission paths, said tunable grating being adjustable to reflect a target wavelength band;
inputting an optical carrier along a first optical transmission path and into said first directional optical transfer device, said first optical transmission path being one of said at least three optical transmission paths, said optical carrier having a transmission wavelength;
outputting said optical carrier from said first directional optical transfer device and along a second optical transmission path, said second optical transmission path being optically coupled to said at least one tunable grating, said second optical transmission path being one of said at least three optical transmission paths;
tracking said transmission wavelength of said optical carrier;
and
dynamically tuning said at least one tunable grating in response to data generated from said tracking of said transmission wavelength of said optical carrier.

5 more elements

Dependencies are inferred from the claim text.

Wavelength tracking in adjustable optical systems

Life of this patent

Wavelength tracking in adjustable optical systems

Life of this patent

Abstract

Claims18