阅读说明：本技术 与硅光子平台集成的自由空间cwdm mux/demux (Free space CWDM MUX/DEMUX integrated with silicon photonics platform ) 是由 马克·彼得森 苏巴尔·萨尼 彼得·德·多比拉里 于 2018-08-10 设计创作，主要内容包括：用于与基于光栅耦合器的硅平台集成的自由空间CWDM MUX/DEMUX的方法和系统可以包括耦合到光子芯片的光学组件。所述光学组件包括芯片顶面上的透镜阵列、倾斜镜、多个透明间隔件和多个薄膜滤波器。所述光学组件可以经由耦合到光学组件的光纤接收包括不同波长的多个光信号的输入光信号，通过多个透明间隔件中的第一个传送多个光信号，使多个光信号中的第一个通过多个薄膜滤波器中相应的一个，同时将多个光信号中的其他光信号反射回多个透明间隔件中的第一个，并向多个第二薄膜滤波器反射多个信号中的其他光信号。(Methods and systems for free-space CWDM MUX/DEMUX integrated with a grating coupler-based silicon platform may include an optical component coupled to a photonic chip. The optical assembly includes a lens array on a top surface of a chip, a tilted mirror, a plurality of transparent spacers, and a plurality of thin film filters. The optical package may receive an input optical signal comprising a plurality of optical signals of different wavelengths via an optical fiber coupled to the optical package, transmit the plurality of optical signals through a first one of a plurality of transparent spacers, pass the first one of the plurality of optical signals through a corresponding one of a plurality of thin film filters, while reflecting others of the plurality of optical signals back to the first one of the plurality of transparent spacers and reflecting others of the plurality of optical signals to a plurality of second thin film filters.)

1. A method for communication, the method comprising:

performing the following steps in an optical assembly coupled to a top surface of a photonic chip, the optical assembly comprising a lens array, a tilted mirror, a plurality of transparent spacers, and a plurality of thin film filters on the top surface of the photonic chip:

receiving an input optical signal via an optical fiber coupled to the optical component, the input optical signal comprising a plurality of optical signals of different wavelengths;

transmitting the plurality of optical signals through a first transparent spacer of the plurality of transparent spacers;

passing a first optical signal of the plurality of optical signals through a respective one of the plurality of thin film filters while reflecting others of the plurality of optical signals back to the first one of the plurality of transparent spacers;

reflecting other ones of the plurality of signals toward a second one of the plurality of thin film filters via a reflective surface of the first one of the plurality of transparent spacers;

passing one of the other of the plurality of optical signals through the second of the plurality of thin film filters; and is

Reflecting the passed optical signal into the photonic chip using the tilted mirror.

2. The method of claim 1, comprising focusing an optical signal received from the optical fiber onto the first thin film filter of the plurality of thin film filters using a silicon lens.

3. The method of claim 1, wherein each thin film filter is configured for one of the plurality of optical signals of a different wavelength.

4. The method of claim 1, wherein the input optical signal is a Coarse Wavelength Division Multiplexed (CWDM) signal.

5. The method of claim 1, wherein the optical assembly comprises: a second lens array, a second tilted mirror, a second plurality of transparent spacers, and a second plurality of thin film filters on a top surface of the photonic chip.

6. The method of claim 5, comprising: receiving a second input optical signal via a second optical fiber coupled to the optical package and a first transparent spacer of the second plurality of transparent spacers, the second input optical signal comprising a second plurality of optical signals of different wavelengths.

7. A system for communication, the system comprising:

an optical assembly coupled to a top surface of the photonic chip, the optical assembly comprising: a lens array on a top surface of the photonic chip, a tilted mirror, a plurality of transparent spacers, and a plurality of thin film filters, the optical assembly operable to:

receiving an input optical signal via an optical fiber coupled to the optical component, the input optical signal comprising a plurality of optical signals of different wavelengths;

transmitting the plurality of optical signals through a first transparent spacer of the plurality of transparent spacers;

passing a first optical signal of the plurality of optical signals through a respective one of the plurality of thin film filters while reflecting others of the plurality of optical signals back to a first transparent spacer of the plurality of transparent spacers;

reflecting other ones of the plurality of signals toward a second one of the plurality of thin film filters via a reflective surface of a first one of the plurality of transparent spacers;

passing one of the other of the plurality of optical signals through a second of the plurality of thin film filters; and is

Reflecting the passed optical signal into the photonic chip using the tilted mirror.

8. The system of claim 7, wherein the optical assembly is operable to focus an optical signal received from the optical fiber onto a first thin film filter of the plurality of thin film filters using a silicon lens.

9. The system of claim 7, wherein each thin film filter is configured for one of the plurality of optical signals at a different wavelength.

10. The system of claim 7, wherein the input optical signal is a Coarse Wavelength Division Multiplexed (CWDM) signal.

11. The system of claim 7, wherein the optical assembly comprises: a second lens array, a second tilted mirror, a second plurality of transparent spacers, and a second plurality of thin film filters on a top surface of the photonic chip.

12. The system of claim 11, wherein the optical assembly is operable to receive a second input optical signal comprising a second plurality of optical signals of different wavelengths via a second optical fiber coupled to the optical assembly and a first transparent spacer of the second plurality of transparent spacers.

13. A method for communication, the method comprising:

performing the following steps at an optical assembly coupled to a top surface of a photonic chip, the optical assembly comprising a lens array, a tilted mirror, a plurality of transparent spacers, and a plurality of thin film filters on the top surface of the photonic chip:

receiving a plurality of optical signals of different wavelengths in the optical assembly from the photonic chip via the lens array;

reflecting the plurality of optical signals to a first one of the transparent spacers using the tilted mirror;

passing at least a first and a second optical signal of the plurality of optical signals through respective first and second thin film filters into a second of the transparent spacers;

passing a third optical signal of the plurality of optical signals through a first one of the transparent spacers into a second one of the transparent spacers without passing through the thin film filter;

reflecting a second signal of the plurality of signals onto the first thin film filter via a reflective surface of a first transparent spacer of the plurality of transparent spacers;

continuously reflecting a third optical signal of the plurality of optical signals between the reflective surface and the thin film filter until the third optical signal of the plurality of optical signals is reflected off the first thin film filter; and is

Coupling the plurality of optical signals into an optical fiber, the optical fiber coupled with the optical component.

14. The method of claim 13, comprising focusing an optical signal into the optical fiber using a silicon lens.

15. The method of claim 13, wherein each of the thin film filters is configured for one of the plurality of optical signals of a different wavelength.

16. The method of claim 13, wherein coupling the plurality of optical signals into the optical fiber generates a Coarse Wavelength Division Multiplexed (CWDM) signal.

17. The method of claim 13, wherein the optical assembly comprises: a second lens array, a second tilted mirror, a second plurality of transparent spacers, and a second plurality of thin film filters on a top surface of the photonic chip.

18. The method of claim 17, comprising: a second plurality of optical signals of different wavelengths is received via the second lens array and reflected to the second plurality of thin film filters using the second tilted mirror via the second plurality of transparent spacers.

19. A system for communication, the system comprising:

an optical assembly coupled to a top surface of the photonic chip, the optical assembly comprising: a lens array on a top surface of the photonic chip, a tilted mirror, a plurality of transparent spacers, and a plurality of thin film filters, the optical assembly operable to:

receiving a plurality of optical signals of different wavelengths in the optical assembly from the photonic chip via the lens array;

reflecting the plurality of optical signals to a first one of the transparent spacers using the tilted mirror;

passing at least a first and a second of the plurality of optical signals through respective first and second thin film filters into a second of the transparent spacers;

passing a third optical signal of the plurality of optical signals through a first one of the transparent spacers into a second one of the transparent spacers without passing through the thin film filter;

reflecting a second signal of the plurality of signals onto the first thin film filter via a reflective surface of a first transparent spacer of the plurality of transparent spacers;

continuously reflecting a third optical signal of the plurality of optical signals between the reflective surface and the thin film filter until the third optical signal of the plurality of optical signals is reflected off the first thin film filter; and is

Coupling the plurality of optical signals into an optical fiber, the optical fiber coupled with an optical component.

20. The system of claim 19, wherein the optical assembly is operable to focus an optical signal into the optical fiber using a silicon lens.

21. The system of claim 19, wherein each of the thin film filters is configured for one of the plurality of optical signals at a different wavelength.

22. The system of claim 19, wherein the plurality of optical signals are coupled into the optical fiber, generating a Coarse Wavelength Division Multiplexed (CWDM) signal.

23. The system of claim 19, wherein the optical assembly comprises: a second lens array, a second tilted mirror, a second plurality of transparent spacers, and a second plurality of thin film filters on a top surface of the photonic chip.

24. The system of claim 23, wherein the optical assembly is operable to receive a second plurality of optical signals of different wavelengths via the second lens array and reflect the second plurality of optical signals of different wavelengths to the second plurality of thin film filters using the second tilted mirror via the second plurality of transparent spacers.

Technical Field

Aspects of the present disclosure relate to electronic assemblies. More particularly, certain implementations of the present disclosure relate to methods and systems for free-space CWDM MUX/DEMUX integrated with a grating coupler-based silicon platform.

Background

Conventional methods for CWDM multiplexing and demultiplexing may be expensive, cumbersome and/or inefficient, e.g., they may be complex and/or time consuming, and/or may have limited responsiveness due to loss.

Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present disclosure, as set forth in the remainder of the present application with reference to the drawings.

Disclosure of Invention

A system and method are provided for a free-space CWDM MUX/DEMUX integrated with a grating coupler-based silicon platform, substantially as set forth more completely in the claims and as shown in and/or described in connection with at least one of the figures.

These and other advantages, aspects, and novel features of the present disclosure, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings.

Drawings

FIG. 1 is a block diagram of a photon-enabled integrated circuit for free-space CWDM MUX/DEMUX integrated with a grating-coupler-based silicon platform according to an example embodiment of the present disclosure;

FIG. 2 illustrates a thin film filter external MUX/DEMUX for coupling to a grating coupler on a photonic chip, according to an example embodiment of the present disclosure;

3A-3C illustrate top, side, and side views of a thin film filter external MUX/DEMUX for coupling to a grating coupler on a photonic chip according to example embodiments of the present disclosure;

fig. 4 illustrates a thin film filter external MUX/DEMUX with horizontal and vertical planar channel separation according to an example embodiment of the present disclosure.

Detailed Description

As used herein, the terms "circuit" and "circuitry" refer to physical electronic components (i.e., hardware) and any software and/or firmware ("code") that may configure, be executed by, or otherwise be associated with the hardware. As used herein, for example, a particular processor and memory may include a first "circuit" when executing a first line or lines of code and may include a second "circuit" when executing a second line or lines of code. As used herein, "and/or" refers to any one or more items in a list connected by "and/or". For example, "x and/or y" refers to any element of the triplets { (x), (y), (< x, y) }. In other words, "x and/or y" means "one or both of x and y". As another example, "x, y, and/or z" refers to any element of the seven-tuple { (x), (y), (z), (x, y), (x, z), (y, z), (x, y, z) }. In other words, "x, y, and/or z" means "one or more of x, y, and z. The term "exemplary", as used herein, is meant to be used as a non-limiting example, illustration, or description. As used herein, the terms "for example" and "such as" list one or more non-limiting examples, or illustrations. As used herein, a circuit or device is "operable" for performing a function, whether the performance of the function is disabled or enabled (e.g., by user-configurable settings, factory trimming, etc.), so long as the circuit or device includes the hardware and code necessary to perform the function (if necessary).

Fig. 1 is a block diagram of a photon-enabled integrated circuit having a free-space CWDM MUX/DEMUX for integration with a grating-coupler based silicon platform according to an example embodiment of the present disclosure. Referring to FIG. 1, optoelectronic devices on a photon-enabled integrated circuit 130 are shown, including optical modulators 105A-105D, photodiodes 111A-111D, monitor photodiodes 113A-113H, and optical devices including coupler 103, optical terminations 115A-115D, and grating couplers 117A-117H. Also shown are electrical devices and circuits including amplifiers 107A-107D, analog and digital control circuitry 109, and control portions 112A-112D. The amplifiers 107A-107D may comprise, for example, transimpedance and limiting amplifiers (TIAs/LAs).

In an example scenario, the photon-enabled integrated circuit 130 includes a CMOS photonics die having a laser component 101 coupled to a top surface of the IC 130. The CW laser In 101 comprises one or more laser assemblies comprising a plurality of semiconductor lasers with isolators, lenses and/or rotators for directing one or more CW optical signals to a coupler 103. In an example scenario, the laser assembly may be multiple laser modules in one laser assembly, or may comprise an array of lasers in a single module, e.g., where a pair of lasers is coupled to each light modulator, one laser being coupled to each arm of the modulator, thereby providing a redundant light source for each transceiver. By coupling redundant lasers to each modulator, yield may be improved, especially when testing the lasers prior to assembly with CMOS die 130 is difficult.

Photon-enabled integrated circuit 130 may comprise a single chip, or may be integrated on multiple dies, e.g., one or more electronic dies and one or more photonic dies.

Optical signals are communicated between the light and the optoelectronic device via optical waveguide 110 fabricated in photonic-enabled integrated circuit 130. Single mode or multimode waveguides may be used in photonic integrated circuits. Single mode operation can be directly connected to optical signal processing and network elements. The term "single mode" may be used for a waveguide supporting a single mode of each of two polarizations (transverse electric (TE) polarization and Transverse Magnetic (TM) polarization), or for a waveguide that is truly single mode and supports only one mode of its polarization as TE, including an electric field parallel to the substrate supporting the waveguide. Two typical waveguide cross sections used include strip waveguides and rib waveguides. The strip waveguides typically comprise a rectangular cross-section, while the rib waveguides comprise a rib cross-section at the top of the waveguide plate. Of course, other waveguide cross-sectional types are also contemplated within the scope of the present disclosure.

Optical modulators 105A-105D comprise, for example, Mach-Zehnder modulators or ring modulators, and are capable of modulating a Continuous Wave (CW) laser input signal. The optical modulators 105A-105D may include high speed and low speed phase modulation sections and be controlled by control sections 112A-112D. The high-speed phase modulation portions of optical modulators 105A-105D may modulate a CW optical source signal with a data signal. The low-speed phase modulation portions of optical modulators 105A-105D may compensate for slowly varying phase factors, such as those caused by mismatch between waveguides, waveguide temperature, or waveguide stress, referred to as passive phase or passive biasing of the MZI.

In an example scenario, a high speed optical phase modulator may operate based on free carrier dispersion effects and may demonstrate a high degree of overlap between the free carrier modulation region and the optical mode. High speed phase modulation of an optical mode propagating in a waveguide is a building block for several types of signal encoding for high data rate optical communications. To maintain the high data rates used in modern optical links, speeds of several Gb/s may be required and can be achieved in integrated silicon photonics by modulating the depletion region of a PN junction placed on a waveguide carrying the optical beam. The overlap between the optical mode and the depletion region of the PN junction is optimized for improved modulation efficiency and minimized loss.

The outputs of light modulators 105A-105D may be optically coupled to grating couplers 117E-117H via waveguides 110. Coupler 103 may comprise, for example, a four-port optical coupler and may be used to sample or separate the optical signals generated by optical modulators 105A-105D, wherein the sampled signals are measured by monitor photodiodes 113A-113H. The unused branches of directional coupler 103 may be terminated by optical terminations 115A-115D to avoid unwanted signal back reflections.

Grating couplers 117A-117H include gratings that are capable of coupling light into and out of photonic-enabled integrated circuit 130. Grating couplers 117A-117D may be used to couple light received from an optical fiber via an optical coupler with integrated optics into photonic enabled integrated circuit 130, and grating couplers 117E-117H may be used to couple light from photonic enabled integrated circuit 130 into an optical fiber. Grating couplers 117A-117H may include Single Polarization Grating Couplers (SPGCs) and/or Polarization Splitting Grating Couplers (PSGCs). In the case of using the PSGC, two input or output waveguides may be used.

The optical fibers may be coupled to the IC 130 using a lens array 121 and an optical assembly 123, for example, the optical assembly 123 including lenses, spacers, mirrors, and thin film filters. These structures will be further described with reference to fig. 2-4.

Photodiodes 111A-111D may convert the optical signals received from grating couplers 117A-117D into electrical signals, which are passed to amplifiers 107A-107D for processing. For example, in another embodiment of the present disclosure, photodiodes 111A-111D may comprise high speed heterojunction phototransistors and may include germanium (Ge) in the collector and base regions for absorption in the 1.3-1.6 μm optical wavelength range and may be integrated on a CMOS silicon-on-insulator (SOI) wafer. In another example scenario, the photodiode may comprise a 4-port high speed photodiode, enabling reception of different channels from two different Polarization Splitting Grating Couplers (PSGCs).

Analog and digital control circuitry 109 may control gain levels or other parameters in the operation of amplifiers 107A-107D, which amplifiers 107A-107D may then transmit electrical signals from photonic-enabled integrated circuit 130. The control sections 112A-112D include electronic circuits capable of modulating the CW laser signal received from the coupler 103. For example, optical modulators 105A-105D may require high-speed electrical signals to modulate the refractive indices in the respective branches of a Mach-Zehnder interferometer (MZI). In an example embodiment, the control portions 112A-112D may include heat sinks and/or source driver electronics, which may implement a bi-directional link with a single laser.

In operation, photonic-enabled integrated circuit 130 may be operable to transmit and/or receive and process optical signals. Optical signals may be received from the optical fibers by grating couplers 117A-117D and converted to electrical signals by photodetectors 111A-111D. For example, the electrical signal may be amplified by a transimpedance amplifier in amplifiers 107A-107D and subsequently transferred to other electronic circuitry (not shown) in photonic-enabled integrated circuit 130.

The integrated photonics platform allows all of the functionality of the optical transceiver to be integrated on a single chip. The optical transceiver chip contains opto-electronic circuits that generate and process optical/electrical signals at the transmitter (Tx) and receiver (Rx) sides, and an optical interface that couples optical signals to and from the optical fiber. The signal processing functions may include: modulating photo-carriers, detecting optical signals, separating or combining data streams, multiplexing or demultiplexing data on carriers having different wavelengths, and equalizing signals to reduce and/or eliminate inter-symbol interference (ISI), which may be a common drawback in optical communication systems.

Photon-enabled integrated circuit 130 may comprise a single electronic/photonic CMOS die/chip or may comprise separate CMOS dies for photonic and electronic functions. The photonic-enabled integrated circuit 130 may be coupled to the optical fiber using a lens array 121 and optics 123, as further illustrated with reference to fig. 2-4.

Due to the wavelength bandwidth of the grating coupler, it may be difficult to integrate CWDM with 20nm pitch with grating coupler based silicon photonics. This problem can be solved using an external MUX/DEMUX using Planar Lightwave Circuit (PLC) technology and/or Thin Film Filters (TFF).

Fig. 2 illustrates a thin film filter external MUX/DEMUX for coupling to a grating coupler on a photonic chip according to an example embodiment of the present disclosure. Referring to fig. 2, an external MUX/DEMUX optical assembly 200 is shown that includes a lens array 201, a mirror 203, spacers 205A-205C, a membrane filter 207, a lens 209, and a fiber stub 211. Also shown is an optical fiber 125 for coupling optical signals to and/or from the optical package 200. The lens array 201 may include a plurality of silicon lenses, for example, operable to focus the optical signal at a desired point having a desired beam width and an angle to the normal. The spacers 205A-205C may comprise glass or similar materials having a desired index of refraction and allowing precise thickness control.

The fiber stub 211 may include mechanical structures for securing the fiber 125 to the optical assembly 200 and may be coupled to the lens 209, e.g., the lens 209 may include silicon. The ferrule 211 may comprise metal or other rigid material for providing mechanical strength to the structure and confinement of the optical fiber 125. The lens 209 is operable to focus light from the optical fiber 125 to the thin film filter 207 in the first spacer 205C or to focus an optical signal received from the thin film filter 207 into the optical fiber 125.

The combination of the spacers 205A-205C and the thin film filter 207 creates a MUX/DEMUX function of the assembly 200, with the lens 209 coupling light in the optical fibers 125 held in the ferrule 211. The spacer 205C coupled to the fiber stub may include a partially coated back surface with a high reflectivity mirror 213 to eliminate back coupling of the signal into the fiber 125 and reflect the signal back to the TFF 207. The spacers 205A-205C may have precise angles and thicknesses for directing the optical signal to the desired lens in the silicon lens array 201 via the angled mirror 203 and to the desired thin film filter 207 for coupling to the optical fiber 125.

Lens 209 may comprise, for example, silicon, which focuses the optical signal from the grating coupler beam via lens array 201 into a parallel collimated beam with a well-selected beam waist to cover the total optical signal passing through the distance to fiber 125. Mirror 203 may comprise a 45 ° total internal mirror that causes the light beam received from lens array 201 to be horizontal or vertical to the signal received from fiber 125.

Thin-film filter 207 may be configured to allow signals having a particular wavelength to pass while removing other wavelengths, the thin-film filter array thereby providing wavelength selection. The thickness and/or material of each filter may be configured for a different wavelength such that each TFF207 may be configured to allow a particular CWDM wavelength to pass.

In operation, a CWDM optical signal comprising a plurality of CWDM wavelength signals may be demultiplexed by coupling the signal from the fiber 125 into the optical package 200. The signal may be focused by a lens onto the first TFF207, where the signal of the passing wavelength of the first TFF will pass, while the remaining wavelengths are reflected back by the back mirror 213 of the spacer 205C and again towards the TFF 207. The next TFF207 will allow the second wavelength CWDM signal to pass while reflecting the remaining wavelengths to mirror 213 and again to the third TFF 207. Finally, the remaining CDWM wavelength signals will be readily passed to the spacer 205A. Each signal passing through TFF207 and the last remaining CWDM wavelengths are reflected down into lens array 201 for focusing onto a grating coupler in the photonics die on which optical package 200 is mounted.

Although three TFFs 207 are shown, representing four CWDM wavelength operations, other numbers are possible. In addition, the optical component 200 may multiplex CWDM signals emitted from a chip on which the MUX/DEMUX component 200 is mounted. Each CWDM wavelength signal may be focused by lens array 201 onto an appropriate point and width and desired shape to be reflected by tilted mirror 203 to TFF207 via spacer 205A. As with the demultiplexing process, CWDM signals of the appropriate wavelength will pass through the TFF207 configured for that wavelength and reflect off mirror 213 and back to the adjacent TFF207 for further reflection. This back and forth reflection continues until each signal is reflected from the first TFF207 into the lens 209, such that each wavelength signal from each optical path is coupled into the spacer 205C and then into the lens 209 for focusing into the fiber 125.

Fig. 3A-3C illustrate top, side, and side views of a thin film filter external MUX/DEMUX for coupling to a grating coupler on a photonic chip according to example embodiments of the present disclosure. Referring to fig. 3A, a top view of the thin film filter external MUX/DEMUX optical assembly 300 is shown, illustrating the paths of different optical signals into corresponding grating couplers on a photonic IC. The MUX/DEMUX optical assembly 300 includes a lens array 201, a mirror 203, spacers 205A-205C, TFF207, a lens 209, and a ferrule 211.

Fig. 3A also shows the optical path of a CWDM signal entering or exiting the fiber in either direction. For example, a CWDM optical signal comprising four CWDM wavelength signals may be received in the optical package 300 via the optical fiber 125 and focused by the lens 209 via the spacer 205B onto the first TFF207, wherein the first CWDM wavelength for which the first TFF207 is configured passes through, while the remaining signals are reflected back to the mirror 213 at the back of the spacer 205B, then to the next TFF207, and so on, until the last CWDM wavelength signal only passes through into the spacer 205A. Each signal entering spacer 205A may then be reflected by mirror 203 down into lens array 201 for focusing onto a grating coupler in the photonic die coupled to optical assembly 300.

Similarly, the side views of FIGS. 3B and 3C illustrate various components, such as the optical fiber 125, the ferrule 211, the spacers 205A-205C, the thin film filter 207, the mirror 203, and the lens array 201. As can be seen in fig. 3C, the lens array 201 may include a convex lens structure 201A in contact with the total internal reflection mirror 203. Angular control in the spacers 205A-205C may be important for proper coupling of the desired signal, and active alignment may be used to align grating couplers in a photonic chip (not shown) below the lens array 201 and for aligning the optical fiber 125 to the assembly 300. The spacing and size may be determined based on the beamwaist requirement for throw distance.

Furthermore, as can be seen in fig. 3B and 3C, the spacers 205A-205C may include multiple layers for thickness, alignment, refractive index, and reflectivity control. The reflectivity of the backside of the spacer 205B adjacent to the lens 209 may be configured to reflect the CWDM signal reflected by the TFF207 back to the TFF207 using the mirror 213. In this manner, CWDM signals that do not pass through a particular TFF207 outside of the passband may be reflected to the next TFF 207. As shown in fig. 3A and 3C, the optical path illustrates a downward reflection of the optical signal received from fiber 125 and/or a lateral reflection of the optical signal received from lens array 201 below. In addition, lens array 201 may focus the optical signals at an angle off normal to the bottom surface of lens array 201 and the top surface of the photonic die receiving the signals to improve coupling efficiency.

In operation, a CWDM optical signal comprising a plurality of CWDM wavelength signals may be demultiplexed by coupling the signal from the fiber 125 into the optical package 300. The signal may be focused by a lens onto the first TFF207, where the signal of the passing wavelength of the first TFF will pass, while the remaining wavelengths are reflected back by the back mirror 213 of the spacer 205C and again towards the TFF 207. The next TFF207 will allow the second wavelength CWDM signal to pass while reflecting the remaining wavelengths to mirror 213 and again to the third TFF 207. Finally, the remaining CDWM wavelength signals will be readily passed to the spacer 205A. Each signal passing through TFF207 and the last remaining CWDM wavelengths are reflected down into lens array 201 for focusing onto a grating coupler in the photonics die on which optical package 300 is mounted.

Although three TFFs 207 are shown, representing four CWDM wavelength operations, other numbers are possible. In addition, the optical component 300 may multiplex CWDM signals emitted from a chip on which the MUX/DEMUX component 300 is mounted. Each CWDM wavelength signal may be focused by the lens array 201 onto an appropriate spot having a desired beam width and shape to be reflected by the mirror 203 via the spacer 205A to the TFF 207. As with the demultiplexing process, CWDM signals of the appropriate wavelength will pass through the TFF207 configured for that wavelength and reflect off mirror 213 and back to the adjacent TFF207 for further reflection. This back and forth reflection continues until each signal is reflected from the first TFF207 into the lens 209, such that each wavelength signal from each optical path is coupled into the spacer 205C and then into the lens 209 for focusing into the fiber 125.

Fig. 4 illustrates a thin film filter external MUX/DEMUX with horizontal and vertical planar channel separation according to an example embodiment of the present disclosure. Referring to fig. 4, an external MUX/DEMUX optical assembly 400 is shown that includes lens arrays 401A and 401B, mirrors 403A and 403B, spacers 405A-405D, TFF407A and 407B, lenses 409A and 409B, ferrules 411A and 411B, and mirrors 413A and 413B. A pair of optical fibers 425A and 425B are also shown. In this example, the dual optical paths illustrated by optical path 1 and optical path 2 enable channel separation in the horizontal direction on the mold surface using thin film filters and associated optics, and channel separation vertically using multiple optical fibers (e.g., fibers 425A and 425B).

The optical elements may be similar to those described previously, but the parallel paths are displaced in the vertical direction (as shown by the space between fibers 425A and 425B) and in the horizontal direction (as shown by the horizontal distance between lens arrays 401A and 401B).

In the illustrated embodiment, mirrors 403A and 403B reflect optical signals coming from or going to vertically split fibers and horizontally split optical signals via TFFs 407A and 407B and mirrors 413A and 413B, as shown in the top view of fig. 3A. The reflected signals may pass into lens arrays 401A and 401B for coupling to respective grating couplers in the photonic IC, or in the output direction, may receive optical signals from grating couplers in the photonic IC and couple the signals to TFFs 407A and 407B for coupling to respective fibers 425A and 425B in ferrules 411A and 411B.

In operation, CWDM optical signals may be demultiplexed by coupling signals from the optical fibers 425A and 425B into the optical package 400, each signal comprising a plurality of CWDM wavelength signals. The signal may be focused by the lenses 409A and 409B onto the first TFF in each set of TFFs 407A and 407B, where the signal of the passing wavelength of the first TFF in each set of TFFs 407A and 407B will pass, while the remaining wavelengths are reflected back, again by the back mirrors 413A and 413B toward the remaining TFFs 407A and 407B. The next TFF of each set of TFFs 407A and 407B allows the second wavelength CWDM signal to pass while reflecting the remaining wavelengths to mirrors 413A and 413B and again to the third TFF in each set of TFFs 407 and 407B. Finally, the remaining CWDM wavelength signals will be easily transferred to the spacers 405A and 405D. Each signal passing through TFFs 407A and 407B and the last remaining CWDM wavelength in each path is reflected down into lens arrays 401A and 401B for focusing onto a grating coupler in the photonic die on which optical package 400 is mounted. Although two sets of three TFFs 407A and 407B are depicted in this example, representing dual four channel CWDM or eight channel CWDM operation, other numbers of channels are possible.

The optical assembly 400 may also multiplex CWDM signals emitted from a chip on which the MUX/DEMUX assembly 400 is mounted. Each CWDM wavelength signal may be focused by lens arrays 401A and 401B onto an appropriate spot having a desired beam width and shape to be reflected by mirrors 403A and 403B to TFFs 407A and 407B via spacers 405A and 405D. As with the demultiplexing process, the CWDM signal of the appropriate wavelength will pass through TFFs 407A and 407B configured for that wavelength and reflect from mirrors 413A and 413B back to adjacent TFFs 407A and 407B for further reflection. This back and forth reflection continues until each signal is reflected off of the first TFF407A or 407B and into the lens 409A or 409B, such that each wavelength signal from each optical path is coupled into the spacers 405C and 405F and then into the lenses 409A and 409B for focusing into the fiber 125.

In example embodiments of the present disclosure, a method and system for free-space CWDM MUX/DEMUX integrated with a grating coupler-based silicon platform is described. The system may include an optical assembly coupled to the top surface of the photonic chip, wherein the optical assembly includes a lens array, a tilted mirror, a plurality of transparent spacers, and a plurality of thin film filters on the top surface of the photonic chip.

The optical assembly is operable to: receiving an input optical signal comprising a plurality of optical signals of different wavelengths via an optical fiber coupled to an optical package; transmitting a plurality of optical signals through a first one of the plurality of transparent spacers; passing a first one of the plurality of optical signals through a corresponding one of the plurality of thin film filters while reflecting others of the plurality of optical signals back to the first one of the plurality of transparent spacers; reflecting other signals of the plurality of signals toward the plurality of second thin film filters via the reflective surface of the first one of the plurality of transparent spacers; passing one other of the plurality of optical signals through a plurality of second thin film filters; and reflecting the passed optical signal into the photonic chip using a tilted mirror.

The optical assembly is operable to focus an optical signal received from the optical fiber onto a first one of the plurality of thin film filters using the silicon lens. Each thin film filter may be configured for one of the different wavelengths of the plurality of optical signals. The input optical signal may be a Coarse Wavelength Division Multiplexed (CWDM) signal. The optical assembly may include a second lens array, a second tilted mirror, a plurality of second transparent spacers, and a plurality of second thin film filters on the top surface of the photonic chip. The optical package is operable to receive a second input optical signal comprising a plurality of second optical signals of different wavelengths via a second optical fiber coupled to the optical package and a first one of a plurality of second transparent spacers.

In another example embodiment of the present disclosure, a method and system for free-space CWDM MUX/DEMUX integrated with a grating coupler-based silicon platform is described. The system may include an optical assembly coupled to the top surface of the photonic chip, wherein the optical assembly includes a lens array, a tilted mirror, a plurality of transparent spacers, and a plurality of thin film filters on the top surface of the photonic chip.

The optical assembly is operable to: receiving a plurality of optical signals of different wavelengths in the optical package from the photonic chip via the lens array; reflecting a plurality of optical signals into a first one of the transparent spacers using a tilted mirror; passing at least first and second optical signals of the plurality of optical signals through respective first and second thin film filters into a second one of the transparent spacers; passing a third one of the plurality of optical signals through the first one of the plurality of transparent spacers and into the second one of the transparent spacers without passing through the thin film filter; reflecting a second one of the plurality of signals onto the first thin film filter via the reflective surface of the first one of the plurality of transparent spacers; continuously reflecting a third of the plurality of optical signals between the reflective surface and the thin film filter until reflected off the first thin film filter; and coupling the plurality of optical signals into an optical fiber coupled to the optical package.

The optical assembly can be operated to focus an optical signal into an optical fiber using a silicon lens. Each thin film filter may be configured for one of the different wavelengths of the plurality of optical signals. Coupling multiple optical signals into an optical fiber may generate a Coarse Wavelength Division Multiplexed (CWDM) signal. The optical assembly may include a second lens array, a second tilted mirror, a plurality of second transparent spacers, and a plurality of second thin film filters on a top surface of the photonic chip. The optical assembly is operable to receive a plurality of second optical signals of different wavelengths via a second lens array and reflect them to a plurality of second thin film filters using a second tilted mirror via a plurality of second transparent spacers.

While the disclosure has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.