PLANAR LIGHTWAVE FILTER WITH MIXED DIFFRACTION ELEMENTS

Abstract

A planar lightwave circuit including a slab waveguide, with a plurality of different diffraction filtering elements optically coupling a plurality of input and output ports, provides various optical functionalities including multiplexing, demultiplexing, diplexer and triplexer. In the basic configuration one or more output ports are optically coupled to an input port via grating filters etching in the cladding of the slab waveguide, and an additional port is optically coupled to the input port via a diffraction grating etched in an endwall of the slab waveguide. A triplexer platform can be provided by optically coupling photo-detectors to two output ports, which receive wavelength channels demultiplexed from an input signal by two cladding etched filters, and by optically coupling a laser to another input port, which launches an outgoing laser signal at the endwall etched grating filter for coupling into the same fiber that launched the original input signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in greater detail with reference to the accompanying drawings which represent preferred embodiments thereof, wherein:

FIG. 1 illustrates a conventional triplexer device utilizing thin film filters;

FIG. 2 illustrates a conventional triplexer device utilizing thin film filters mounted on a semiconductor substrate;

FIG. 3 illustrates a planar lightwave circuit according to the present invention for demultiplexing optical signals;

FIG. 4 illustrates one possible set of transmissions to the output ports of the planar lightwave circuit of FIG. 3;

FIG. 5 illustrates another possible set of transmissions to the output ports of the planar lightwave circuit of FIG. 3;

FIG. 6 illustrates a planar lightwave circuit according to the present invention for multiplexing optical signals;

FIG. 7 illustrates a planar lightwave circuit according to the present invention for demultiplexing two sets of optical signals with different channel spacing;

FIG. 8 illustrates a planar lightwave circuit according to the present invention for demultiplexing and multiplexing optical signals;

FIG. 9 illustrates a planar lightwave circuit according to the present invention providing bidirectional triplexer functionality;

FIG. 10 illustrates a planar lightwave circuit according to the present invention providing bi-directional diplexer functionality; and

FIG. 11 illustrates a planar lightwave circuit according to the present invention providing wavelength locking functionality to a laser.

Claims

1. A planar lightwave circuit device comprising: a slab waveguide including a core region;a first port for launching a first input optical signal into the slab waveguide;a second port optically coupled with the first port for outputting at least a first portion of the input optical signal from the slab waveguide;a third port optically coupled to the first port;a first planar filter formed in the slab waveguide for redirecting the first portion of the input optical signal to the second port; anda concave reflective element having optical power formed in an end wall of the slab waveguide optically coupling the first port to the third port and enabling light to be focused therebetween.

2. The device according to claim 1, wherein the first filter comprises a concave distributed Bragg reflector for redirecting and refocusing the first portion of the first input optical signal to the second port.

3. The device according to claim 2, wherein the reflective element comprises a concave diffraction grating formed in the end wall of the slab waveguide for filtering and refocusing at least one wavelength channel between the first and third ports.

4. The device according to claim 3, wherein the diffraction grating separates and refocuses at least one wavelength channel from the first input optical signal onto the third port.

5. The device according to claim 3, wherein the diffraction grating multiplexes a wavelength channel from a second optical signal launched from the third port onto the first port.

6. The device according to claim 3, wherein the diffraction grating has a spectral response at least five times wider than that of the first filter.

7. The device according to claim 1, further comprising: a fourth port optically coupled with the first port; and a second planar filter formed in the slab waveguide region optically coupling the first port with the fourth port.

8. The device according to claim 7, wherein the first input optical signal includes a plurality of wavelength channels; wherein the first portion comprises a first wavelength channel, which the first filter demultiplexes; wherein the concave reflective element redirects a second wavelength channel from the first input optical signal to the third port; and wherein the second filter demultiplexes a third wavelength channel from the first input optical signal and redirects the third wavelength channel to the fourth port.

9. The device according to claim 8, further comprising a fifth port optically coupled to the first port; wherein the concave reflective element comprises a concave diffraction grating, which also demultiplexes and focuses a fourth wavelength channel from the first input optical signal to the fifth port.

10. The device according to claim 9, wherein the first and second filters demultiplex channels with a first channel spacing; and wherein the concave diffraction grating demultiplexes channels with a second channel spacing different than the first channel spacing.

11. The device according to claim 7, wherein the first input optical signal includes a plurality of wavelength channels; wherein the first portion comprises a portion of each of the wavelength channels, which the first filter directs to the second port; wherein the reflective element redirects a second wavelength channel to the third port; and wherein the second filter demultiplexes a third wavelength channel from the first input optical signal and redirects the third wavelength channel to the fourth port.

12. The device according to claim 7, wherein the first input optical signal includes a plurality of wavelength channels; wherein the first portion comprises a first wavelength channel, which the first filter redirects to the second port, while passing a second wavelength channel; wherein the second filter redirects a third wavelength channel launched via the fourth port to the second port, while passing a fourth wavelength channel; and wherein the reflective element redirects and focuses the second and fourth wavelength channels onto the third port.

13. The device according to claim 7, wherein the input optical signal includes a plurality of wavelength channels; wherein the first portion comprises a first wavelength channel, which the first filter demultiplexes; wherein the second filter demultiplexes and redirects a second wavelength channel from the first input optical signal to the fourth port; and wherein the reflective element multiplexes a third wavelength channel launched in a second input optical signal via the third port onto the first port.

14. The device according to claim 13, further comprising: a first photo-detector optically coupled to the second port for converting the first wavelength channel to a first electrical signal; a second photo-detector optically coupled to the fourth port for converting the second wavelength channel to a second electrical signal; and a laser optically coupled to the third port for generating an optical signal comprising the third wavelength channel.

15. The device according to claim 14, wherein the first and second filters each comprise a concave distributed Bragg reflector for redirecting and refocusing the first and second wavelength channels to the second and fourth ports, respectively; and wherein the reflective element comprises a diffraction grating formed in the end wall of the slab waveguide for refocusing the third wavelength channel, with a desired channel width at least five times wider than the first and second channels, from the third port onto the first port.

16. The device according to claim 1, further comprising a laser optically coupled to the first port; wherein the second port is in the same location as the first port, whereby the first planar filter redirects and refocuses a first portion of the input optical signal back to the laser for locking the wavelength thereof at a desired wavelength, and passes a remainder of the input optical signal to the concave reflective element; and wherein the concave reflective element focuses the remainder of the input optical signal onto the third port.

17. A planar lightwave circuit device comprising: a slab waveguide including a core region;first port for launching an input optical signal into the slab waveguide;a second port for outputting a first portion of the input optical signal;a first concave distributed Bragg reflector filter formed in the slab waveguide for redirecting and refocusing the first portion of the input optical signal onto the second port, and for passing a second portion of the input optical signal;a third port for outputting the second portion of the input optical signal; anda concave diffraction grating, having an order of zero or higher, formed in an endwall of the slab waveguide for focusing light between the first and third ports.

18. The device according to claim 17, further comprising: a fourth port; and a second concave distributed Bragg reflector filter for optically coupling the first port with the fourth port.

19. The device according to claim 18, further comprising a laser optically coupled to the fourth port for launching an output signal at the concave diffraction grating for output the first port.

20. A wavelength locker comprising: a slab waveguide included a core region;a first port for optically coupling to a laser, which launches an input optical signal into the slab waveguide;a first concave distributed Bragg reflector filter formed in the slab waveguide for redirecting and refocusing a first portion of the input optical signal back to the first port for locking the wavelength thereof at a desired wavelength, and for passing a remainder of the input optical signal;a second port optically coupled with the first port for outputting the remainder of the input optical signal from the slab waveguide; anda concave reflective element formed in an end wall of the slab waveguide optically coupling the first port to the third port for redirecting and refocusing the remainder of the input optical signal to the second port.

21. The device according to claim 20, wherein the reflective element comprises a concave diffraction grating for filtering out unwanted portions of the remainder of the input optical signal.