Optical waveguides – With optical coupler – Plural
Reexamination Certificate
1999-07-02
2001-05-29
Ullah, Akm E. (Department: 2874)
Optical waveguides
With optical coupler
Plural
Reexamination Certificate
active
06240223
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a tunable optical routing device.
2. Description of the Related Art
Optical communications networks that use wavelength division multiplexing (WDM) require optical routing devices, or add/drop devices, to select one or more wavelength channels from a multiple wavelength channel signal and provide the selected wavelength channel(s) to a subscriber. The add/drop devices also add one or more wavelength channels received from a subscriber to the multiple wavelength channel signal. Thus, a subscriber can receive from an add/drop device a particular wavelength channel and the information contained in the channel, e.g., telephone voice information, add communication information to the channel, and send the channel back to the add/drop device so that the added communication information can be transmitted to another party.
Current add/drop devices are either only capable of adding or dropping a single fixed wavelength channel, or adding or dropping a fixed set of multiple wavelength channels. Devices capable of adding or dropping a fixed set of multiple wavelength channels are not capable of adding or dropping the multiple channels using a single add or drop port, and must instead use multiple add or drop ports, one port for each wavelength channel. In addition, current add/drop devices cannot be tuned to select different sets of wavelength channels. That is, current devices can only select a single fixed channel or a fixed set of channels. Re-tuning of the devices requires that filters or other components of the devices be replaced so that another or additional channels can be added or dropped.
SUMMARY OF THE INVENTION
The invention provides a wavelength routing device that is capable of receiving multiple wavelength channels at each of two input ports and of outputting two different sets of wavelength channels at each of two ports such that the output sets can include channels that were input at both input ports. For example, if channels A, B and C are input at a first input, and channels D, E and F are input at the second input, one set of channels A, B and F can be output at a first output and another set of D, E and C can be output at the second output. The device can be selectively tuned to adjust which received channels are output at each output port.
The invention also provides a tunable add/drop device that can be tuned to selectively add or drop a desired wavelength or set of multiple wavelengths. The add/drop device can be tuned to simultaneously add or drop multiple selected channels using single add and drop ports.
In one aspect of the invention, an input signal received at a first input port of a wavelength routing device includes a plurality of wavelength channels and is incident on at least two filters. The filters can be thin film interferometer filters or other suitable wavelength selection devices. At least one mirror in the device causes a wavelength channel that passes through one of the filters to be directed back through the filter. The mirror can also prevent at least one wavelength channel received at another input port from being incident on the filter. By selectively redirecting wavelength channels to again pass through filters and allowing wavelength channels to pass through filters unimpeded, a selected wavelength channel or channels can be output at one of two desired outputs of the device.
The mirror or mirrors that cause wavelength channels to be redirected through filters in the device can be movable metallic mirrors or other reflective structures. Thus, when a mirror is moved to a first blocking position, the mirror can cause light that passes through a corresponding filter to be redirected and again pass back through the filter, or prevent light from being incident on the filter at all. When the mirror is moved to a second non-blocking position, wavelength channels can be allowed to pass unimpeded through the filter or otherwise be allowed to be incident on the filter. The mirror or mirrors can also comprise structures or devices that can be made selectively transparent or reflective, rather than moved. For example, a mirror can include a field effect transistor that is transparent when in a first state, and a metallic reflector when switched into a second state. Other devices, such as 2×2 optical switches, can be used to cause light to be either re-directed to pass through a corresponding filter or to prevent light from being incident on the corresponding filter altogether.
In one aspect of the invention, a wavelength routing device has a first optical path that communicates with a first output port and a second optical path that communicates with a second output port. At least one filter allows one or more selected wavelength channels to pass from one path to the other. At least one optical device, such as a reflective structure, prevents the one or more selected wavelength channels from passing from one path to the other. Thus, desired wavelengths can be allowed to transfer from one optical path to the other and be output at a desired output port.
These and other aspects of the invention will be apparent and/or obvious from the following description.
REFERENCES:
patent: 5537258 (1996-07-01), Yamazaki et al.
patent: 5617243 (1997-04-01), Yamazaki et al.
patent: 5923683 (1999-07-01), Morioka et al.
AT&T Corp.
Ullah Akm E.
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