Tunable Optical Module for Optical Communication
Light of at least two wavelengths is collimated in a forward path towards a reflector and light of at least one of the wavelengths is focused and detected in a return path, using in both paths a lens unit including a first convex surface and a second surface. A diffraction element diffracts the collimated light of the at least two wavelengths into different wavelength components. The reflector is moved so that one or more of the different wavelength components will be focused by the lens unit in the return path and detected. The second surface reflects the light of the at least two wavelengths from an input port towards the first convex surface and the first convex surface collimates the reflected light of the at least two wavelengths in the forward path, or the first convex surface focuses the one or more wavelength components towards the second surface that reflects the one or more wavelength components to an output port in the return path. The first convex surface can be replaced by a GRIN lens performing the focusing and collimating functions.
This invention relates generally to the optical components used in optical communication networks, and specifically to a hybrid optical module that combines an electrically-tunable optical filter, optical source(s) and a novel lens unit.
Optical communication networks are built by combining sub-systems, modules, or components which perform specific functions, including the function of selecting or removing a particular wavelength or group of wavelengths. Briefly, multiple optical signals can be transmitted simultaneously by encoding them in separate carrier wavelengths similar to the way radio stations use different carrier frequencies to which the end user tunes. Encoding multiple signals using different carrier wavelengths is referred to as Dense Wavelength Division Multiplexing (DWDM). A general description of optical networking functions and applications can be found in “Introduction to DWDM Technology”, by S. Kartalopoulos, Wiley-Interscience, 2000. In this application, “multiple” means “more than one.”
DWDM Technology has been widely deployed in long haul communications networks. Recently, this technology started migrating to short-haul optical communications networks, for applications such as Digital TV delivery, Fiber-to-the-Home (FTTH), Internet access, Local Area Networks, back-haul connections for cellular base stations, Wi-Fi hotspots, and other forms of broadband access. In prior networks, it has been typical for only one specified wavelength to reach the receiver of an end user, who also sends a single wavelength back to the network. This transmitter-receiver (transceiver) module at the end user is called a bi-directional wavelength add-drop module. However, with increasing demands for bandwidth and network flexibility, multiple wavelengths may be broadcast or delivered to an end user, and then one wavelength (or potentially a small range of wavelengths) is selected by the end user. There is, therefore, a strong demand to provide an integrated module that combines a photodetector with a tunable optical filter, to select particular wavelength(s) from a multiple-wavelength DWDM optical signal, which also includes a transmitter or a group of transmitters to send a different wavelength or a band of different wavelengths back to the network. Furthermore, to meet the requirements and needs of short-distance optical systems, these tunable transceivers have to be compact, reliable, inexpensive, and producible on a large scale. There is also a demand for sub-assemblies of the above system that may not include all of the components of the system to serve as building blocks of the system.
SUMMARY OF THE INVENTIONOne embodiment of the invention is directed to a tunable optical device, comprising a reflector, an input port and an output port and a lens unit collimating light of at least two wavelengths from the input port in a forward path and focusing light of at least one of the at least two wavelengths to the output port in a return path. The lens unit includes a first convex surface and a second surface. The device also has at least one diffraction element that is located in the forward path and/or the return path between the lens unit and the reflector and that diffracts the collimated light of the at least two wavelengths into different wavelength components; and an actuator that moves the reflector so that one or more of the different wavelength components will travel in the return path to the lens unit and be focused to the one output port by the lens unit. The second surface reflects the light of the at least two wavelengths from the input port towards the first convex surface and the first convex surface collimates the reflected light of the at least two wavelengths in the forward path, or the first convex surface focuses the one or more wavelength components towards the second surface that reflects the one or more wavelength components to the output port in the return path.
Another embodiment of the invention is directed to an optical tuning method, comprising collimating light of at least two wavelengths from an input port in a forward path towards a reflector and focusing light of at least one of the at least two wavelengths to an output port in a return path, using a lens unit including a first convex surface and a second surface. At least one diffraction element located in the forward path and/or the return path between the lens unit and the reflector is used to diffract the collimated light of the at least two wavelengths into different wavelength components. The reflector is moved so that one or more of the different wavelength components will travel in the return path to the lens unit and be focused to the one output port by the lens unit. The second surface reflects the light of the at least two wavelengths from the input port towards the first convex surface and the first convex surface collimates the reflected light of the at least two wavelengths in the forward path, or the first convex surface focuses the one or more wavelength components towards the second surface that reflects the one or more wavelength components to the output port in the return path.
Still another embodiment of the invention is directed to a tunable optical device, comprising a reflector, an input port, an output port and a lens unit collimating light of at least two wavelengths from the input port in a forward path and focusing light of at least one of the at least two wavelengths to the output port in a return path, the lens unit including a focus/collimation element and a surface. The device includes at least one diffraction element that is located in the forward path and/or the return path between the lens unit and the reflector and that diffracts the collimated light of the at least two wavelengths into different wavelength components; and an actuator that moves the reflector so that one or more of the different wavelength components will travel in the return path to the lens unit and be focused to the one output port by the lens unit. The surface reflects the light of the at least two wavelengths from the input port towards the focus/collimation element and the focus/collimation element collimates the reflected light of the at least two wavelengths in the forward path, or the focus/collimation element focuses the one or more wavelength components towards the surface that reflects the one or more wavelength components to the output port in the return path.
All patents, patent applications, articles, books, specifications, other publications, documents and things referenced herein are hereby incorporated herein by this reference in their entirety for all purposes. To the extent of any inconsistency or conflict in the definition or use of a term between any of the incorporated publications, documents or things and the text of the present document, the definition or use of the term in the present document shall prevail.
Identical components are labeled by the same numerals in this application. The optical paths and the angles of diffraction in the figures are not drawn to scale.
DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTSThe present invention utilizes a lens unit, which can be a novel lens or novel lens assembly, having the functions of processing optical signals for filtering, attenuation, detection, and transmission, together in a single module. The lens is used to integrate an optical tunable filter, attenuator, photodetector, diode laser(s), and an optical port, in a compact unit.
The reflection of the multi-wavelength signal at slanted surface 212 is described in more detail in
The incident rays represented by 203A, 203B, and 203C in
The MEMS mirror, mounted on a substrate 223, has two rotational axes, 225 and 226. The axis 225 is used to selectively reflect one or more wavelengths or wavelength ranges to a photodetector 241, while having the beam remain in the optical plane x-y. In some cases, there is also a need to attenuate the signal strength for the photodetector. Thus the other rotational axis 226 is used to tune the optical beam slightly out of the x-y plane, in order to reduce or attenuate the optical power of the beam that reaches the photodetector 241.
A more detailed structural view of the photodetector package 240 shown in
To make the tunable receiver more convenient for installation inside a Multi-Source Agreement (MSA) pluggable cage assembly such as Compact Form-factor Pluggable (CFP), and Small Form Factor Pluggable (SFP) cages it may be necessary to orient the ferrule 202 of the optical fiber 201 such that it lines up with the dome lens 210, with the ferrule 202 protruding out of the front panel of MSA pluggable cage assemblies. All of the components of the device 220 may be contained within a compact container shown in dotted line in
In addition to detecting one or more wavelength out of multiple wavelengths, the end clients or customers in an optical network often need to add a signal back to the network, for a variety of purposes, including network supervision.
In order to make the assembly of tunable optical add-drop module even more compact, the laser diode package 617 can be re-oriented to be side-by-side with the photodetector package 240, as shown in
Instead of coating the dichroic filter on the slanted surface 212, as shown in
Instead of using a separate substrate 668, coated with a dichroic filter 667 (as shown in
While the invention has been described above by reference to various embodiments, it will be understood that changes and modifications may be made without departing from the scope of the invention, which is to be defined only by the appended claims and their equivalents. For example, lens 210 with a dome surface 215 as shown in
Claims
1. A tunable optical device, comprising:
- an input port and an output port;
- a lens unit collimating light of at least two wavelengths from the input port in a forward path and focusing light of at least one of said at least two wavelengths to the output port in a return path, said lens unit including a first convex surface and a second surface;
- a reflector;
- at least one diffraction element that is located in the forward path and/or the return path between the lens unit and the reflector and that diffracts said collimated light of said at least two wavelengths into different wavelength components; and
- an actuator that moves the reflector so that one or more of said different wavelength components will travel in said return path to the lens unit and be focused to said one output port by the lens unit;
- wherein the second surface reflects the light of the at least two wavelengths from the input port towards the first convex surface and the first convex surface collimates the reflected light of the at least two wavelengths in the forward path, or said first convex surface focuses the one or more wavelength components towards said second surface that reflects the one or more wavelength components to the output port in the return path.
2. The device of claim 1, wherein when the second surface reflects the light of the at least two wavelengths from the input port towards the first convex surface and the first convex surface collimates the reflected light of the at least two wavelengths in the forward path, said first convex surface focuses the one or more wavelength components to the output port in the return path without involving said second surface.
3. The device of claim 1, wherein said first convex surface collimates the light of the at least two wavelengths from the input port in the forward path without involving the second surface and focuses the one or more wavelength components towards said second surface that reflects the one or more wavelength components to the output port in the return path.
4. The device of claim 1, wherein the actuator that moves the reflector so that an intensity of said one or more wavelength components is controlled to be of a desired value.
5. The device of claim 4, wherein the actuator rotates the reflector about two different axes, wherein rotation of the reflector about one of the axes causes selection from the at least two wavelengths the one or more wavelength components that travel in the return path, and rotation about the other one of the axes causes attenuation of said one or more of said different wavelength components.
6. The device of claim 1, wherein the at least one diffraction element diffracts said collimated light of the at least two wavelengths from the lens unit into different wavelength components towards the reflector, and said reflector reflects the different wavelength components towards the at least one diffraction element so that the different wavelength components are diffracted.
7. The device of claim 1, further comprising an optical source providing light of one or more desired wavelengths to the input port, so that the device functions as a transceiver.
8. The device of claim 7, further comprising a dichroic filter coating on said second surface to reflect light from the input port and transmit light from the optical source.
9. The device of claim 8, further comprising a second reflector that reflects light from the optical source to the dichroic filter coating.
10. The device of claim 7, further comprising a dichroic filter between the convex surface and the at least one diffraction element to transmit light from the input port and reflect light from the optical source.
11. The device of claim 10, wherein the dichroic filter is a coating on the at least one diffraction element.
12. The device of claim 1, further comprising a photodetector package that includes an aperture and a photodetector aligned to the aperture for receiving light directed to the output port.
13. The device of claim 12, wherein the input port is movable to align a desired wavelength component of the diffracted different wavelength components with the aperture, and wherein the aperture does not transmit the diffracted different wavelength components that are not the desired wavelength component to the photodetector.
14. The device of claim 1, said lens unit including a lens element with said first convex surface having an optical axis and said second surface is at a slanted angle to and on one side of the optical axis.
15. The device of claim 1, said lens unit including a convex lens and a transparent block with a surface at a slanted angle to an axis of the convex lens.
16. The device of claim 1, further comprising an optical fiber ferrule at the input port and a photodetector package at the output port, and a container that contains the optical fiber ferrule, the lens unit, the at least one diffraction element, the reflector, the actuator and the photodetector package.
17. The device of claim 16, further comprising an optical source providing light of one or more desired wavelengths to the input port so that the device functions as a transceiver, said container also containing the optical source.
18. The device of claim 1, wherein said second surface is a reflecting surface.
19. An optical tuning method, comprising:
- collimating light of the at least two wavelengths from an input port in a forward path towards a reflector and focusing light of at least one of said at least two wavelengths to an output port in a return path, using a lens unit including a first convex surface and a second surface;
- using at least one diffraction element located in the forward path and/or the return path between the lens unit and the reflector to diffract said collimated light of the at least two wavelengths into different wavelength components; and
- moving the reflector so that one or more of said different wavelength components will travel in said return path to the lens unit and be focused to said one output port by the lens unit;
- wherein the second surface reflects the light of the at least two wavelengths from the input port towards the first convex surface and the first convex surface collimates the reflected light of the at least two wavelengths in the forward path, or said first convex surface focuses the one or more wavelength components towards said second surface that reflects the one or more wavelength components to the output port in the return path.
20. The method of claim 19, wherein when the second surface reflects the light of the at least two wavelengths from the input port towards the first convex surface and the first convex surface collimates the reflected light of the at least two wavelengths in the forward path, said first convex surface focuses the one or more wavelength components to the output port in the return path without involving said second surface.
21. The method of claim 19, wherein said first convex surface collimates the light of the at least two wavelengths from the input port in the forward path without involving the second surface and focuses the one or more wavelength components towards said second surface that reflects the one or more wavelength components to the output port in the return path.
22. The method of claim 19, wherein the input port is moved to align a desired wavelength component of the diffracted different wavelength components with an aperture and a photodetector, and wherein the aperture does not transmit the diffracted different wavelength components that are not the desired wavelength component to the photodetector, and wherein said input port is fixed in position after said alignment.
23. The method of claim 19, further comprising passing the light directed to the output port through an aperture to a photodetector aligned to the aperture for detection.
24. The method of claim 23, further comprising adjusting a dimension of the aperture to determine a bandwidth of the wavelength component(s) that passes the aperture to the photodetector.
25. A tunable optical device, comprising:
- an input port and an output port;
- a lens unit collimating light of at least two wavelengths from the input port in a forward path and focusing light of at least one of said at least two wavelengths to the output port in a return path, said lens unit including a first convex surface and a second surface;
- a reflector;
- at least one diffraction element that is located in the forward path and/or the return path between the lens unit and the reflector and that diffracts said collimated light of the at least two wavelengths into different wavelength components; and
- an actuator that moves the reflector so that one or more of said different wavelength components will travel in said return path to the lens unit and be focused to said one output port by the lens unit;
- wherein said first convex surface collimates the light of the at least two wavelengths from the input port in the forward path without involving the second surface and focuses the one or more wavelength components towards said second surface that reflects the one or more wavelength components to the output port in the return path.
26. The device of claim 25, further comprising an optical source providing light of one or more desired wavelengths to the input port, so that the device functions as a transceiver.
27. The device of claim 26, further comprising a dichroic filter between the convex surface and the at least one diffraction element to transmit light from the input port and reflect light from the optical source.
28. The device of claim 27, wherein the dichroic filter is a coating on the at least one diffraction element.
29. A tunable optical device, comprising:
- an input port and an output port;
- a lens unit collimating light of at least two wavelengths from the input port in a forward path and focusing light of at least one of said at least two wavelengths to the output port in a return path, said lens unit including a focus/collimation element and a surface;
- a reflector;
- at least one diffraction element that is located in the forward path and/or the return path between the lens unit and the reflector and that diffracts said collimated light of said at least two wavelengths into different wavelength components; and
- an actuator that moves the reflector so that one or more of said different wavelength components will travel in said return path to the lens unit and be focused to said one output port by the lens unit;
- wherein the surface reflects the light of the at least two wavelengths from the input port towards the focus/collimation element and the focus/collimation element collimates the reflected light of the at least two wavelengths in the forward path, or said focus/collimation element focuses the one or more wavelength components towards said surface that reflects the one or more wavelength components to the output port in the return path.
30. The device of claim 29, wherein said focus/collimation element comprises a convex lens or a GRIN lens and a transparent block with a surface at a slanted angle to an axis of the convex or GRIN lens.
Type: Application
Filed: Oct 28, 2015
Publication Date: May 4, 2017
Inventors: Ho-Shang Lee (El Sobrante, CA), Yu-Sheng Yang (Kaohsiung City)
Application Number: 14/925,719