Wavelength division multiplexing coupler with loss element
A method and system for adjusting power at output ports of a wavelength division multiplexing (WDM) coupler. A loss element may be placed at one or more of the output ports of the WDM coupler. The loss element may have a filter characteristic that matches the temperature sensitivity coefficient of the WDM coupler. The filter characteristic may reject power at one of the two output ports as a function of temperature. As a result, the loss element may balance the power at the output ports of the WDM coupler despite temperature variations.
1. A wavelength division multiplexing coupler comprising:
a coupling section;
at least one input port;
a plurality of output ports;
a loss element;
wherein the at least one input port is coupled to the coupling section by a wave guide;
wherein the plurality of output ports is coupled to the coupling section by a plurality of wave guides; and
wherein the loss element has a filter characteristic that substantially matches a temperature sensitivity coefficient of the wavelength division multiplexing coupler and adjusts power output at one of the output ports to maintain a desired splitting ratio with temperature variation.
2. The wavelength division multiplexing coupler of claim 1 , wherein the loss element is a fiber grating.
3. The wavelength division multiplexing coupler of claim 1 , wherein the loss element has a filter characteristic comprising a pass band and a rejection band that shifts as a function of temperature.
4. The wavelength division multiplexing coupler of claim 3 , wherein the filter characteristic shifts at −5 ppm/C.
5. The wavelength division multiplexing coupler of claim 1 , wherein the wavelength division multiplexing coupler has a temperature sensitivity coefficient of +5 ppm/C.
6. The wavelength division multiplexing coupler of claim 1 , wherein the wavelength division multiplexing coupler has a temperature sensitivity coefficient of between −20 ppm/C and +20 ppm/C.
7. The wavelength division multiplexing coupler of claim 1 , wherein the power output of the at least one of the plurality of output ports is proportional to a shift in wavelength of light input into the at least one input port.
8. The wavelength division multiplexing coupler of claim 1 , wherein the light input to the at least one input port is form a light source selected from the group consisting of a fiber optic light source and a semiconductor light source.
9. The wavelength division multiplexing coupler of claim 1 , wherein the power output at the at least one output port is balanced.
10. The wavelength division multiplexing coupler of claim 1 , wherein the power output of the at least one of the plurality of output ports is proportional to a shift in wavelength of light input into the at least one input port.
11. The wavelength division multiplexing coupler of claim 1 , wherein the light input to the at least one input port is form a light source selected from the group consisting of a fiber optic light source and a semiconductor light source.
12. A method comprising:
determining a temperature sensitivity coefficient of a wavelength division multiplexing coupler;
passing light from a light source through at least one input port of the wavelength division multiplexing coupler; and
adjusting, as a function of temperature, power output at a plurality of output ports of the wavelength division multiplexing coupler, the power output being adjusted by a loss element at at least one of the plurality of output ports, the loss element having a filter characteristic that matches the temperature sensitivity of the wavelength division multiplexing coupler.
13. The method of claim 12 , wherein the filter characteristic is defined by a rejection band and a pass band that shift as the temperature changes.
14. The method of claim 12 , wherein determining the temperature sensitivity coefficient comprises:
measuring the power output at the plurality of output ports of the wavelength division multiplexing coupler; and
adjusting a wavelength of the light from the light source so that the power output at the plurality of output ports is balanced.
15. The method of claim 12 , wherein the light source is selected from the group consisting of a fiber optic light source and a semiconductor light source.
16. A wavelength division multiplexing coupler comprising:
two waveguides joined at a coupling section;
at least one input port on one of the waveguides on a first side of the coupling section;
each waveguide having an output port on a second side of the coupling section;
a temperature varying loss element coupled between the coupling section and one of the output ports of one of the waveguides, wherein the loss element has a filter characteristic that substantially matches a temperature sensitivity coefficient of the wavelength division multiplexing coupler such that a desired splitting ratio between the waveguides is maintained with temperature variations for a selected wavelength of light.
17. The wavelength division multiplexing coupler of claim 16 , wherein the loss element is a fiber grating.
18. The wavelength division multiplexing coupler of claim 16 , wherein the loss element has a filter characteristic comprising a pass band and a rejection band that shifts as a function of temperature.
19. A wavelength division multiplexing coupler comprising:
two waveguides joined at a coupling section;
at least one input port on one of the waveguides on a first side of the coupling section;
each waveguide having an output port on a second side of the coupling section;
means for maintaining a desired splitting ratio between the waveguides with temperature variations for a selected wavelength of light, said means including a loss element having a filter characteristic that matches the temperature sensitivity of the wavelength division multiplexing coupler.