WO2002086568A2 - Optical interferometer for demultiplexing an optical sound - Google Patents
Optical interferometer for demultiplexing an optical sound Download PDFInfo
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- WO2002086568A2 WO2002086568A2 PCT/US2002/012535 US0212535W WO02086568A2 WO 2002086568 A2 WO2002086568 A2 WO 2002086568A2 US 0212535 W US0212535 W US 0212535W WO 02086568 A2 WO02086568 A2 WO 02086568A2
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29346—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by wave or beam interference
- G02B6/29358—Multiple beam interferometer external to a light guide, e.g. Fabry-Pérot, etalon, VIPA plate, OTDL plate, continuous interferometer, parallel plate resonator
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
- G02B6/29395—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device configurable, e.g. tunable or reconfigurable
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
Definitions
- the present invention relates generally to the field of optical communications systems. More specifically, the present invention discloses an optical interferometer for demultiplexing an optical signal.
- Wavelength division multiplexing is a commonly used technique that allows the transport of multiple optical signals, each at a slightly different wavelength, over an optical fiber.
- the ability to carry multiple signals on a single fiber allows that fiber to carry a tremendous amount of traffic, including data, voice, and digital video signals.
- ITU International Telecommunications Union
- G.mcs proposes a frequency grid which specifies various channel spacings including 100 GHz and 200 GHz.
- Interferometers can be used as wavelength routers to multiplex or demultiplex optical signals for WDM communications.
- an interferometer When performing the multiplexing function, an interferometer combines two input WDM signals, each containing sets of optical channels, into a single, more densely spaced output signal.
- an interferometer When used as a demultiplexer, an interferometer separates an input WDM signal containing a plurality of optical channels at different wavelengths into two, more widely spaced sets of channels.
- interferometers can be employed to divide the spectral space evenly with alternating optical channels being directed to each output port (i.e., odd wavelength channels 1, 3, 5, 7, etc. are directed to a first output port, while even wavelength channels 2, A, 6, etc. are directed to a second output port).
- This function has sometimes been called an optical interleaver.
- This function is inherently bi- directional and can also be used to multiplex two sets of input channels (containing the even and odd channels, respectively) into a single output signal.
- One of the difficulties in making a practical interferometer is the stabilization of the optical path length in the device, which affects the wavelength stability of the device.
- Materials in the interferometer can change index of refraction and physical dimension when subjected to temperature and mechanical perturbations.
- others have resorted to temperature control of the optical cavity, compensation of material index change by making composites of dissimilar materials, and birefringent interferometers.
- the present invention discloses an optical interferometer architecture that is stable, compact, and requires no temperature control.
- One embodiment of the present invention is an apparatus for processing an optical signal that includes a tunable optical element and a reflective element.
- the tunable optical element receives an input signal at an incidence angle and separates the input signal into a first beam having a first optical path length and a second beam having a second optical path length. The difference between the first optical path length and the second optical path length is based at least in part upon the incidence angle of the input signal.
- the reflective element reflects the first beam and the second beam such that the first beam interferes with the second beam to produce a first output signal and a second output signal.
- the first output signal comprises a first subset of wavelength channels from the input signal and the second output signal comprises a second subset of wavelength channels from the input signal.
- Another embodiment of the present invention is a method for processing an optical signal that includes receiving an input signal at an incidence angle.
- the method proceeds by separating the input signal into a first beam having a first optical path length and a second beam having a second optical path length.
- the difference between the first optical path length and the second optical path length is based at least in part upon the incidence angle of the input signal.
- the method concludes by interfering the first beam with the second beam to produce a first output signal and a second output signal.
- the first output signal comprises a first subset of wavelength channels from the input signal and the second output signal comprises a second subset of wavelength channels from the input signal.
- Yet another embodiment of the present invention is an optical system that includes a demultiplexer network, an optical component coupled to the demultiplexer network, and a multiplexer network coupled to the optical component.
- the demultiplexer network demultiplexes an input WDM signal into a plurality of wavelength channels and includes a tunable optical element and a reflective element.
- the optical component processes a portion of the wavelength channels.
- the multiplexer network multiplexes a portion of the wavelength channels to generate an output WDM signal.
- An interferometer of the present invention provides an optical element that may be dynamically tuned to control the optical path lengths of the beams used in the operation of the interferometer.
- the wavelength channel spacings of the resulting signals may be dynamically controlled whether the interferometer is used as a demultiplexer or a multiplexer.
- the interferometer comprises a bi-directional device that allows for tunability, stability, and robust operation in a compact architecture.
- FIGURE 1 illustrates one embodiment of an interferometer using a tunable optical element and a reflective element in accordance with the present invention
- FIGURE 2 illustrates another embodiment of the interferometer
- FIGURE 3 illustrates the interferometer using a reflective element that isolates input and output signals
- FIGURE 4 illustrates one embodiment of the interferometer that includes a first tunable optical element and a second tunable optical element
- FIGURE 5 illustrates one embodiment of the interferometer that includes a tunable optical element, a mirror, and a resonator
- FIGURE 6 illustrates one embodiment of the interferometer that includes a tunable optical element, a first resonator, and a second resonator
- FIGURE 7 illustrates a cascaded architecture of interferometers
- FIGURE 8 illustrates an optical networking architecture using the interferometers.
- FIGURE 1 illustrates an interferometer 5 that includes a tunable optical element 10 and a reflective element 50.
- interferometer 5 can be used to multiplex or demultiplex optical signals for WDM communications.
- interferometer 5 When used as a demultiplexer, interferometer 5 separates an input WDM signal 30 containing a plurality of optical channels at different wavelengths into two, more widely spaced sets of channels in signals 34 and 36.
- interferometer 5 When performing the multiplexing function, interferometer 5 combines two input WDM signals 34 and 36, each containing sets of optical channels, into a single, more densely spaced output signal 30.
- element 10 may be dynamically tuned to control the optical path lengths traveled by the beams used in the operation of interferometer 5.
- Tunable optical element 10 comprises two parallel, transparent plates 12 and 14 that are separated by a gap 16 measuring a predetermined distance, D, using, in one embodiment, spacers 18.
- a reflective region 22 comprises at least a portion of the inner surface of the first plate 12.
- a partially reflective region 24 covers at least a portion of the inner surface of second plate 14. Any of a wide variety of conventional coating processes can be used to create the reflective and partially reflective regions 22 and 24 on the surfaces of the plates 12 and 14, respectively.
- discrete optical elements or layers can be attached to the plates 12 and 14 to create regions 22 and 24.
- Reflective element 50 comprises any suitable number and combination of mirrors, resonators, etalons, reflective gratings, prisms, filters, or any other suitable optical component or device that is operable to reflect some or all of an optical beam to element 10.
- interferometer 5 In operation of interferometer 5 as a demultiplexer, element 10 receives an input signal 30.
- Input signal 30 comprises a wavelength division multiplexed (WDM) optical signal.
- WDM wavelength division multiplexed
- signal 30 includes multiple channels, each channel with its own range of wavelengths or frequencies.
- channel refers to a particular range of wavelengths or frequencies that define a unique information signal. Each channel may or may not be evenly spaced from adjacent channels.
- Input signal 30 passes through the first plate 12 and is incident on the partially reflective region 24 in a predetermined non-normal orientation (i.e., at an angle of incidence, ⁇ ). This produces a first beam 31 that is transmitted by the partially reflective region 24 and exits through the second plate 14. A portion of the input signal 30 is also reflected by the partially reflective region 24 to create a second beam 32. This second beam 32 is then reflected by the reflective region 22 on the first plate 12 so that it also passes through the second plate 14. The first and second beams 31 and 32 are parallel to one another as they exit the second plate 14 and propagate toward reflective element 50. A difference in the optical path lengths between beams 31 and 32 results due to the internal reflections of the second beam 32 within the element 10.
- the optical path length traveled by a beam 31 or 32 is defined as the summation of the optical thicknesses of all parts in the path, such as, for example, plate 14 and gap 16.
- the optical thickness of a part, such as plate 14 or gap 16 is defined as the physical thickness of that part multiplied by the index of refraction of the intermediate material.
- beams 31 and 32 emitted by element 10 provide a technical advantage to interferometer 5.
- the difference in the optical path lengths between beams 31 and 32 are not sensitive to a change in distance between element 10 and element 50 since such a change impacts the optical path lengths traveled by both beams 31 and 32 substantially equally.
- This provides for easier alignment of element 10 with respect to element 50 during the manufacture of interferometer 5 as well as a more stable operation of interferometer 5.
- Reflective element 50 reflects beams 31 and 32 back along their respective optical paths through element 10, so that the reflected beams 31 and 32 interfere at the partially reflective region 24 to produce output signals 34 and 36.
- the combination of reflection and transmission of beams 31 and 32 at reflective region 24 introduces a phase shift (e.g., a II phase shift) between the interfering beams 31 and 32 causing a first spectral component of input signal 30 to be output as signal 34 and a second spectral component of input signal 30 to be output as signal 36.
- a phase shift e.g., a II phase shift
- even wavelength channels from input signal 30 may be output as signal 34 and odd wavelength channels from input signal 30 may be output as signal 36.
- Regions 22 and 24 of element 10 are generally arranged on the inner surfaces of the parallel plates 12 and 14 as illustrated in FIGURE 1. Because of this construction, beams 31 and 32 exiting the element 10 have traveled the same distance tlirough plate 14. Therefore, the optical path length difference between the two beams 31 and 32 is independent of the material properties of plates 12 and 14.
- the optical path length difference, AL may be characterized by the following equation: where:
- AL is the optical path length difference between beams 31 and 32; D is the thickness of gap 16; n gap is the index of refraction of the material within gap 16, such as, for example, air; and ⁇ is the angle of incidence of the input signal 30.
- the space between the plates 12 and 14 is gap 16 and a fixed separation is maintained between the plates 12 and 14 by a set of spacers 18.
- Spacers 18 can be made of a low-expansion material such as Zerodur or ULE glass, both of which have a negligible amount of dimensional change with temperature. Therefore, the thickness of gap 16, D, is kept constant over a large range of temperature.
- the index of refraction of air is slightly temperature-dependent in an open environment (e.g., at constant air pressure). This dependence can be removed by enclosing the interferometer 5 in a sealed, air-tight enclosure which can be controlled to change the pressure selectively.
- the element 10 in FIGURE 1 has an optical path length difference, AL , that is generally temperature-independent.
- the optical path length difference, AL can be tuned by changing the incidence angle, ⁇ , or by adjusting the pressure in the gap 16 and, hence, the index of refraction of the material within the gap 16.
- the incidence angle, ⁇ may be adjusted by changing the path of signal 30 or by rotating the element 10 with respect to the path of signal 30. Therefore, a distance, D, may be selected for gap 16 that roughly achieves a particular wavelength channel spacing for signals 34 and 36.
- the incidence angle, ⁇ , and/or the index of refraction of the material within gap 16, n gap may then be adjusted to fine tune the wavelength channel spacings of signals 34 and 36.
- interferometer 5 The ability to roughly estimate a particular wavelength channel spacing for signals 34 and 36 combined with the ability to then fine tune this wavelength channel spacing results in a robust manufacturing process and subsequent operation of interferometer 5.
- the following description details the operation of interferometer 5 as a multiplexer. For the purposes of this portion of the description, what was originally referred to as output signals 34 and 36 will be referred to as input signals 34 and 36. Similarly, input signal 30 will be referred to as output signal 30.
- Element 10 receives input signals 34 and 36.
- Input signal 36 passes through the first plate 12 and is incident on the partially reflective region 24 in a predetermined non- normal orientation (i.e., at an angle of incidence, ⁇ ).
- a portion of the input signal 36 is also reflected by the partially reflective region 24 to create a second beam 32.
- This second beam 32 is then reflected by the reflective region 22 on the first plate 12 so that it also passes through the second plate 14.
- the first and second beams 31 and 32 are parallel to one another as they exit the second plate 14 and propagate toward reflective element 50.
- Input signal 34 passes through second plate 14 and is incident on the partially reflective region 24 at an angle of incidence (not shown). This produces a third beam 31' that is reflected by the partially reflective region 24 and exits through plate 14. A portion of input signal 34 is also transmitted by the partially reflective region 24 to create a fourth beam 32'. This fourth beam 32' is then reflected by the reflective region 22 on the first plate 12 so that it also passes through the second plate 14. The third and fourth beams 31' and 32' are parallel to one another as they exit the second plate 14 and propagate toward reflective element 50. In the embodiment illustrated in FIGURE 1, first beam 31 and third beam 31' follow the same optical path toward reflective element 50 and have the same optical path length as each other.
- second beam 32 and fourth beam 32' also follow the same optical path toward reflective element 50 and have the same optical path length as each other.
- Reflective element 50 reflects beams 31 and 32, and beams 31' and 32', back along their respective optical paths through element 10.
- reflected beam 31 interferes with beam 32 and reflected beam 31' interferes with beam 32' to produce output signal 30.
- the combination of reflection and transmission of beams 31, 32, 31', and 32' at reflective region 24 introduces a phase shift (e.g., a II phase shift) between the interfering beams 31, 32, 31', and 32' causing the spectral component of input signal 34 to combine with the spectral component of input signal 36 in output signal 30.
- a phase shift e.g., a II phase shift
- interferometer 5 may combine two input WDM signals 34 and 36, each containing one or more sets of optical channels, into a single, more densely spaced output signal 30.
- interferometer 5 operating as a demultiplexer
- the optical path lengths traveled by beams 31, 32, 31', and 32' and the appropriate differences between these optical path lengths may be adjusted to adjust the operational characteristics of interferometer 5.
- interferometer 5 comprises a bi- directional device that allows for tunability, stability, and robust operation in a compact architecture.
- FIGURE 2 illustrates another embodiment of the interferometer 5 in which the tunable optical element 10 uses a reflective geometry.
- the input signal 30 passes through the second plate 14 and is incident on the partially reflective region 24 on the inner surface of the second plate 14. A portion of the input signal 30 is reflected by the partially reflective region 24 and exits through the second plate 14 to produce the first beam 31. The remainder of the input signal 30 is transmitted through the partially reflective region 24 and the gap 16, and is then reflected by the reflective region 22 through the second plate 14 to produce the second beam 32.
- the remainder of operation for the embodiment illustrated in FIGURE 2 is substantially similar to that of FIGURE 1.
- FIGURE 3 illustrates another embodiment of the interferometer 5 that includes reflective element 52 to isolate output signal 36 from input signal 30.
- Reflective element 52 comprises a mirror, a prism, or any other suitable optical component that redirects the optical path of output signal 36 as it propagates from element 10.
- input signal 30 propagates toward element 10 along a path that avoids reflective element 52 and is processed into output signals 34 and 36 as described above.
- Element 10 is positioned with respect to reflective element 52 such that output signal 36 is incident upon and reflected by reflective element 52 away from the source of input signal 30.
- FIGURE 4 illustrates another embodiment of interferometer 5 that includes a first tunable optical element 10 and a second tunable optical element 60.
- element 10 a first tunable optical element
- element 60 a second tunable optical element 60.
- element 60 is constructed similar to element 10.
- element 60 comprises two parallel plates 62 and 64 separated by a gap 66 using spacers 68.
- Element 60 also includes a partially reflective region 72 and a reflective region 74 on portions of the inner surfaces of the plates 62 and 64, respectively.
- element 10 operates as described above with regard to FIGURE 1.
- second beam 32 exiting element 10 passes through the first plate 62 of element 60 and is reflected by reflective region 74 onto the partially reflective region 72 on the inner surface of the first plate 62 of element 60.
- First beam 31 exiting element 10 passes through the first plate 62 of element 60 and strikes the partially reflective region 72 so that beams 31 and 32 interfere at the partially reflective region 72 to produce output beams 76 and 78.
- the combination of reflection and transmission of beams 31 and 32 at partially reflective region 72 introduces a phase shift (e.g., a II phase shift) between the interfering beams 31 and 32 causing a first spectral component of input signal 30 to be output as signal 76 and a second spectral component of input signal 30 to be output as signal 78.
- a phase shift e.g., a II phase shift
- even wavelength channels from input signal 30 may be output as signal 76 and odd wavelength channels from input signal 30 may be output as signal 78.
- a particular advantage of the embodiment of interferometer 5 illustrated in FIGURE 4 is that signals 76 and 78 are forward propagating such that they are inherently isolated from input signal 30. This provides advantages in packaging and the arrangement of input and output ports for interferometer 5.
- element 60 may also introduce a predetermined difference in the optical path lengths between the beams 31 and 32 before they strike the partially reflective coating 72. Therefore, by tuning one or both of elements 10 and 60, the optical path lengths of beams 31 and 32 may be controlled.
- the wavelength channel spacings of signals 76 and 78, as well as the center wavelengths of each respective channel may be selectively determined and adjusted.
- FIGURE 5 illustrates one embodiment of interferometer 5 in which reflective element 50 comprises a combination of a mirror 80 and a resonator 82.
- Resonator 82 may comprise a Gires-Tournois etalon with front and back layers 84 and 86 separated by an intermediate material in a gap having a predetermined optical thickness.
- mirror 80 is integrated with resonator 82 such that mirror 80 is disposed on the inner surface of the front layer 84.
- mirror 80 may be arranged separate from resonator 82.
- a partially reflective region 88 is disposed on the inner surface of the front layer 84.
- a highly reflective region 90 is disposed on the inner surface of the back layer 86.
- the spacers 92 of resonator 82 are made of low thermal expansion material. Other types of resonator or etalon structures could be readily substituted.
- element 10 operates as described above with regard to FIGURE 1. Thereafter, second beam 32 exiting element 10 propagates toward and is reflected by mirror 80. A portion of first beam 31 is reflected by partially reflective region 88. The remaining portion of beam 31 propagates toward and is reflected by reflective region 90. The arrangement of partially reflective and reflective regions 88 and 90 associated with resonator 82 results in multiple reflections of beam 31 within the resonator 82.
- the resonator 82 reflects substantially all of the incident optical power back regardless of wavelength, but the group delay of the reflected light is strongly dependent on wavelength.
- the two reflected beams 31 and 32 from resonator 82 and mirror 80 retrace their respective optical paths and interfere at the partially reflective region 24 of element 10 to produce output beams 42 and 44.
- a reflective element 52 may be added to the interferometer 5 of FIGURE 5 in order to isolate input signal 30 from output signal 44.
- the combination of reflection and transmission of beams 31 and 32 at reflective region 24 introduces a phase shift (e.g., a II phase shift) between the interfering beams 31 and 32 causing a first spectral component of input signal 30 to be output as signal 42 and a second spectral component of input signal 30 to be output as signal 44.
- a phase shift e.g., a II phase shift
- even wavelength channels from input signal 30 may be output as signal 42 and odd wavelength channels from input signal 30 may be output as signal 44.
- the arrangement of partially reflective and reflective regions 88 and 90 associated with resonator 82 results in multiple reflections of beam 31 within the resonator 82.
- the phase function of the reflected beam 31 becomes non- linear due to the multiple reflections of beam 31 within resonator 82.
- the relative phase shift between the two interfering beams 31 and 32 remains roughly constant over the spectral passband resulting in a flat top waveform for output signals 42 and 44.
- the distance, D, of gap 16 of element 10 is controlled such that the optical path length difference between beams 31 and 32 introduced by element 10 is approximately one half of the optical thickness of resonator 82.
- the pass bands and rejection bands of interferometer 5 are arranged at the appropriate wavelength channel spacings to generate the desired output signals 42 and 44.
- the reflective element 50 illustrated in FIGURE 5 can be modified as shown in the cross-sectional view provided in FIGURE 6 to include a first resonator 82 and a second resonator 92 that essentially replaces mirror 80.
- This modified reflective element 50 contains partially reflective regions 94 and 96 on the inner surface of the front layer 84, and a highly reflective region 90 on the inner surface of the back layer 86.
- the reflectivity of region 90 is set to be 100%.
- the reflectivities of regions 94 and 96 can be varied to adjust the passband, isolation, and dispersion of the output waveforms.
- part of the highly reflective region 90 overlays an additional layer of material 98, such as silicon dioxide. This additional layer 98 has a thickness of approximately ⁇ /4 at the optical wavelength of interest.
- each resonator 82 and 92 is the physical thickness of the gap between the reflective regions multiplied by the refractive index of the material within the gap, such as air, plus the contributions from regions 84, 94, and 96. If the contributions from regions 84, 94, and 96 are substantially equal among resonators 82 and 92, the additional layer of material 98 causes the optical thickness of resonator 92 to be ⁇ /4 less than the optical thickness of resonator 82.
- a single pass optical path length traveled by beam 32 propagating in resonator 92 is ⁇ /4 less than a single pass optical path length traveled by beam 31 propagating in resonator 82 if the contributions from regions 84, 94, and 96 are substantially equal among resonators 82 and 92.
- FIGURE 6 is illustrated with material 98 associated with resonator 92, it should be understood that the layer of material 98 could be deposited on the inner surface of back layer 86 of resonator 82 such that the optical thickness of resonator 82 is ⁇ /4 less than the optical thickness of resonator 92.
- the difference in the optical thicknesses of the resonators 82 and 92 results in the center wavelength of resonator 92 being offset relative to the center wavelength of resonator 82 by approximately one half of the free spectral range (FSR) of both the resonators.
- the FSR of each resonator is defined as the period of the resonator's complex reflectivity. For example, if the free spectral range of both resonators is approximately 50 GHz, then the center wavelength of resonator 92 is offset by approximately 25 GHz relative to the center wavelength of resonator 82. This causes the resonance frequencies of resonator 92 to match that of the anti-resonance frequencies of resonator 82.
- This arrangement of the resonators' center wavelengths can significantly reduce chromatic dispersion in interferometer 5, while keeping a flat-top passband and good isolation among output signals 42 and 44.
- FIGURE 7 illustrates a cascaded architecture 100 of optical filters.
- a first stage of architecture 100 may include an optical filter 102.
- a second stage of architecture 100 may include optical filters 110a and 110b, which are collectively referred to as optical filters 110.
- Third stage of architecture 100 may include optical filters 120a, 120b, 120c, and 120d, which are collectively referred to as optical filters 120.
- Optical filters 102, 110, and 120 may comprise any combination and arrangement of optical filters that employ any suitable conventional optical filtering technology (e.g., fiber bragg gratings, thin film filters, arrayed waveguide grating, etc.) and any suitable embodiment of interferometer 5 illustrated in FIGURES 1-6.
- filter 102 comprises a 50 GHz interferometer 5 that receives a 50 GHz spaced dense wavelength division multiplexed (DWDM) signal 105 and generates an odd-channel 100 GHz spacing DWDM signal 115 and an even channel 100 GHz spacing signal 117.
- Two 100 GHz filters 110a and 110b are used to produce a 200 GHz spaced signal 131 carrying wavelengths ⁇ , and ⁇ 5 , a signal 129 carrying wavelengths ⁇ 3 and ⁇ 7 , a signal 127 carrying wavelengths ⁇ 2 and ⁇ 6 , and a signal 125 carrying wavelengths ⁇ 4 and ⁇ g .
- DWDM dense wavelength division multiplexed
- a third stage of filters 120a-d are used to produce the individual channels ⁇ , , through ⁇ 8 on outputs 141, 149, 145, 153, 143, 151, 147, and 155 respectively.
- Signals 115, 117, 125, 127, 129, and 131 may be referred to as intermediate input signals and/or intermediate output signals with respect to a particular filter 102, 110, or 120.
- the wavelength channel spacings of the signals are dynamically tunable.
- the operation of the device significantly reduces chromatic dispersion while keeping a flat-top passband for each channel and good isolation among channels.
- FIGURE 7 illustrates architecture 100 having three stages of filters to demultiplex a DWDM signal 105 having eight wavelength channels, it is contemplated that architecture 100 may have any suitable number of stages to demultiplex a DWDM signal 105 having any suitable number of wavelength channels. Moreover, FIGURE 7 is detailed with respect to demultiplexing a 50 GHz spaced DWDM signal 105 for illustrative purposes only. It is contemplated that a DWDM signal 105 having any suitable channel spacing (12.5 GHz, 50 GHz, 100 GHz, 200 GHz, etc.) may be processed by the architecture 100 of filters. Additionally, although the description of architecture 100 is detailed with respect to a demultiplexing function, it should be understood that it can also perform a multiplexing function upon individual wavelength channels to produce one or more DWDM signals.
- FIGURE 8 illustrates one embodiment of an optical networking architecture 200 that includes an optical network 205 coupled to a demultiplexer network 210, filters 250, switch fabrics 260, regulators 270, filters 280, and a multiplexer network 230.
- any suitable embodiment of interferometer 5 illustrated in FIGURES 1-6 may be incorporated into architecture 200, such as in demultiplexer network 210 and/or multiplexer network 230.
- architecture 200 may be configured differently and/or may include additional or fewer components without departing from the scope of the present invention.
- Optical network 205 comprises any combination and arrangement of routers, bridges, hubs, gateways, switches, multiplexers, demultiplexers, transmitters, amplifiers, receivers, couplers, isolators, circulators, filters, detectors, wavelength converters, add/drop devices, or any other appropriate optical networking components.
- Optical network 205 may include portions of a long-haul network, a metropolitan network, and/or a local/access network.
- Demultiplexer network 210 and multiplexer network 230 each comprise an appropriate arrangement of filters.
- demultiplexer network 210 comprises filters 212, 214, 216, 218, and 220.
- filters 212-220 may comprise any suitable embodiment of interferometer 5 illustrated in FIGURES 1-6 to perform a demultiplexing function.
- multiplexer network 230 may comprise filters 232, 234, 236, 238, and 240.
- filters 232-240 may comprise any suitable embodiment of interferometer 5 illustrated in FIGURES 1-6 to perform a multiplexing function.
- Filters 250 and 280 comprise gratings, Bragg gratings, Fiber gratings, Fiber
- Bragg gratings Fabry-Perot filters, Thin-Film filters, interferometers, arrayed waveguide gratings, tunable filters, or any other optical device that process and differentiate among optical signals based upon wavelength.
- Switch fabrics 260 comprise switches and/or routers.
- switch fabrics 260 comprise add/drop switch arrays.
- Regulators 270 comprise any suitable device that adjustably regulate the optical power level of an optical channel.
- demultiplexer network 210 receives input signal 30 from network 205.
- Demultiplexer network 210 and filters 250 separate input signal 30 into an array of spatially separated wavelength channels. This is generally done by progressively demultiplexing input signal 30 into intermediate signals, such as, for example, intermediate signals 222a-b, 224a-b, 226, 228a-b, and 229a-b which may be referred to as intermediate input signals and/or intermediate output signals with respect to a particular filter 212, 214, 216, 218, and 220.
- the spacing of each spatially separated wavelength channel may be dynamically tuned.
- each wavelength channel may have a flat-top passband, good isolation from other channels, and low chromatic dispersion.
- Switch fabrics 260 process the spatially separated channels to perform a switching and/or routing function.
- a switch fabric 260 may comprise an add/drop switch array that selectively routes chamiels from the input ports to its drop ports; substitutes channels from the add ports in place of the dropped channels; and routes the remaining input channels and the added channels to the output ports of the add/drop switch array.
- This combination of demultiplexer network 210, filters 250 and add/drop switch arrays 260 allows any combination of input channels to be replaced with any combination of add channels.
- the array of output channels from the switch fabrics 250 pass through regulators 270 which adjustably regulate the optical power level of each channel.
- a selected subset of the channels associated with input signal 30 pass directly from demultiplexer network 210 to multiplexer network 230 in "express lanes.”
- a second array of filters 280 and a multiplexing network 230 combine the output channels so that they can be transmitted as a DWDM output signal 290.
- intermediate signals such as, for example, intermediate signals 242a-b, 244a-b, 246a-b, 248, and 249a-b which may be referred to as intermediate input signals and/or intermediate output signals with respect to a particular filter 232, 234, 236, 238, and 240.
Description
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Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
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US09/840,524 US6621632B2 (en) | 2001-04-23 | 2001-04-23 | Optical interferometer for demultiplexing an optical signal |
US09/840,363 | 2001-04-23 | ||
US09/840,524 | 2001-04-23 | ||
US09/840,363 US20020154313A1 (en) | 2001-04-23 | 2001-04-23 | Optical interferometer for multiplexing optical signals |
Publications (1)
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WO2002086568A2 true WO2002086568A2 (en) | 2002-10-31 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/US2002/012535 WO2002086568A2 (en) | 2001-04-23 | 2002-04-19 | Optical interferometer for demultiplexing an optical sound |
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WO (1) | WO2002086568A2 (en) |
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2002
- 2002-04-19 WO PCT/US2002/012535 patent/WO2002086568A2/en not_active Application Discontinuation
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