`
`jc685 U. S. PTO
`
`1111111111111111111111 111111111111111111
`
`02/17/00
`The Commissioner of Patents and Trademarks
`Washington, D.C. 20231
`U.S.A
`
`PROVISIONAL APPLICATION COVER SHEET
`
`This is a request for filing a PROVISIONAL APPLICATION under 37 CFR 1.53 (b) (2)
`
`File No: 10-329 US PROV
`
`Surname:
`
`Given name:
`
`Residence Address:
`
`Inventors/ Applicants
`
`JT'BOUEVITCH Oleg
`':!;'•
`•='<
`;==DUCELLIER
`Thomas
`i,_!. :-
`:J.JTOMLINSON W. John
`
`' . ~OLBOURNE Paul
`
`L.t.
`i- -
`iff
`!:r i
`
`2336 Shanegal Crescent, Gloucester, Ontario, Canada, Kl V 9P2
`
`415 Besserer Street, Ottawa, Ontario, Canada, KIN 6B9
`
`Unit 1, 68 Lovers Lane, Princeton, N.J. U.S.A., 08540
`
`45D Woodridge Drive, Nepean, Ontario, Canada, K2G 3Y6
`
`TITLE OF THE INVENTION
`
`ADD-DROP MULTIPLEXOR
`
`Correspondence Address:
`
`Mr. Wesley L. Strickland
`Lacasse & Associates
`2001 Jefferson Davis Highway
`Suitte 806
`Arlington, Virginia 22202
`U.S.A
`
`Number of pages:
`Application:
`
`Number of Pages:
`
`13
`
`0001
`
`Capella 2004
`Ciena/Coriant/Fujitsu v. Capella
`IPR2015-00816
`
`
`
`Method of Payment:
`A cheque is enclosed to cover the Provisional Filing Fee in the amount of$150.00 US.
`
`The invention was not made by an agency of the United States Government or under contract with an
`agency of the United States Government
`
`Please charge any additional fees or credit overpayment to Deposit Account No: 20-0345.
`
`Date::L.~~
`
`Respectfully submitted,
`
`~ -z._u. 3~~~
`Randy W. Lacasse
`Regn No: 34,368
`
`200 1 Jefferson Davis Highway
`!j!Suite 806
`~Arlington, VA 22202
`::u.s.A.
`t~iJ
`!.J
`;~Tel:
`;~rax:
`!:i:;
`13 Encl.
`!~/mmc
`·=
`I"U
`
`(703) 415 1015
`(703) 415 1017
`
`0002
`
`
`
`The basic arrangement of proposed COADM module is shown in Figure 1.
`A pair of circulators is used to separate input I output and add/drop signals
`(not shown).
`
`Mirror
`
`Diffraction
`grating
`
`Mirror
`
`~
`~
`
`L..----' t:: v
`
`LC
`array
`
`r/
`~
`~
`~
`
`Switch
`element
`
`Input/output
`Add/Drop
`
`Figure 1.
`
`The front end micro-optics design is shown in Figures 2a, b.
`
`: . ; .
`
`!'"V
`I
`•
`j::o!l
`
`Fiber tube
`
`Figure 2a.
`
`PMD
`
`Half wave
`plate
`
`Birefringent
`element
`
`The light from input fiber is collimated with a microlens. The polarization
`diversity arrangement is used to provide two sub beams at the same
`(horizontal) polarization. A plate, made of the same material as the
`birefringent element, is inserted into upper sub beam for PMD
`compensation. An alternative PMD free front end design is shown in
`Figure 2b.
`
`HaJfy,-ave
`plate
`
`Halfwave
`plate
`
`Fiber tube
`
`Figure 2b.
`
`Birefringent
`elements
`
`0003
`
`2
`
`
`
`In the following Figure 3, the optical layout is explicitly shown. A single mirror
`is used to provide light focussing I collimation. The diffraction grating is
`located at the focus of the mirror. Since the input beams are collimated, the
`light is essentially focussed on the grating. The 1/e2 spot size at the grating,
`2cot, and the 1/e2 beam diameter, 2ro2, at the microcollimator are related in the
`following way:
`
`(1)
`
`It follows from Eq. (1) that one can tune the spot size on the grating and the
`resulting spectral resolution by changing the beam size at microcollimator. It
`should also be kept in mind that, by symmetry, the spot size at LC array is
`equal to the spot size at microcollimator; that, in its turn, dictates
`requirements on the LC array pixel size.
`
`tF
`
`More detailed design exists and can be provided if needed.
`
`Microcollimator
`
`F1
`·=
`
`Liquid crystal array
`
`Figure 3.
`
`Figures 4a and 4b below illustrate how the LC array can be used to provide
`switching between pass through and add I drop states. The optical system
`shown in Figures 1 and 3 delivers the light beams from microcollimators to
`the LC array with no or little additional spot expansion. Since there is a
`diffraction grating in the intermediate focal plane, the light at LC plane will be
`dispersed in wavelength. In Figures 4a and 4b, the dispersion direction is
`perpendicular to the plane of paper.
`
`0004
`
`3
`
`
`
`Liquid crystal
`array element
`in "ON" state
`
`Port 1
`
`Port 2
`
`Liquid crystal
`array element
`in "OFF" state
`
`!D :
`
`In
`[)ron
`Add
`Out
`
`beam splitter
`
`In
`Droo
`Add
`Out
`
`Figure 4a.
`
`Liquid crystal
`array element
`in "ON" state
`
`Liquid crystal
`array element
`in "OFF" state
`
`' .
`L~
`
`In
`Drop
`Add
`Out
`
`Port 1
`
`*--c=J
`~~==
`Port2
`
`Figure 4b.
`
`:n :
`
`In
`Droo
`Add
`Out
`
`prism
`
`The LC cell in "OFF" state rotates polarization by 90 degrees. In "ON" state,
`polarization is not rotated. It is seen from Figures 4a and 4b that in "OFF"
`state the light paths of two ports are interchanged. In "ON" state of LC pixel,
`the light is reflected back into respective port. Since every spectral channel is
`passed through an independently controlled pixel, a full reconfigurability of all
`40 or more channels is obtained. Further, the arrangement of Figure 4b has
`additional advantage of low PMD since the respective positions of two sub
`beams originating from each port does not change upon switching.
`
`With respect to LC cell type, the twisted nematic (TN) cell is a preferable
`candidate since it has a very small residual birefringence in " ON" state. Since
`birefringence is small, a very high contrast ratio (>35 dB) can be obtained and
`maintained over the wavelength and temperature range.
`
`0005
`
`4
`
`
`
`Another embodiment of the switch geometry is shown in Figure 5. In Figure 5,
`the birefringent element is placed before the LC cell.
`
`ADD/DROP
`
`PASS
`
`I t~
`
`Polarization diversity
`
`J4
`
`LC
`rt/2
`
`LCO
`
`Polarization diversity
`
`Figure 5.
`
`LC cell works as a reflective variable retarder.
`
`This invention relates to an add-drop multiplexing circuit that in a first
`preferred embodiment is based on a system that utilizes polarized light. A
`front end described heretofore in Figs. 2a and 2b serves to provide the
`required polarized light. The system shown in Fig. 3 is a preferred
`embodment wherein light is launched and received from two micro lenses
`which serve as input /output ports. The system is a 4-f system and a curved
`mirror has at its focal plane the microlenses, a reflective diffraction grating,
`and an array of element in the form of switches. Although the priniciple
`embodiment described relates to an multiplexor/demultiplexor circuit in the
`form of an add/drop circuit, the invention also lends itself to being used in
`equalization schemes. In such an embodiment an array of detectors (not
`shown) is provided about or near to the switches. The switches described
`heretofore serve to route an incoming signal back to one of the ports from
`which it was launched or alternatively to the other port in dependence upon
`control signals provided to the switch.
`
`Although it is preferred to have a single mirror as shown in the embodiment of
`Fig. 3 more than one mirror can be used. Notwithstanding, if a single mirror is
`used the device will have fewer alignment problems and will have less loss.
`In fact much of the advantage of this design versus a conventional 4f system
`using separate lenses is afforded due to the fact that critical matching of
`components is obviated. A single mirror is used in both directions to and from
`the ports via the switch. Furthermore, if the mirror is mounted to a fused
`silica base and it itself is made of fused silica the entire structure will be quite
`insensitive to small temperature fluctuations.
`
`0006
`
`5
`
`
`
`Although a single mirror and a reflective grating is preferred, using a
`transmissive grating with a second mirror is possible.
`
`0007
`
`6
`
`
`
`' '
`1 !
`l
`·....::...:
`
`i~
`1::::::
`
`CLAIMS
`
`1. A 4-f optical system for multiplexing or demultiplexing an optical signal compnsmg:
`
`reflective means having a focal plane;
`
`at least two ports disposed to provide or receive the optical signal or a portion thereof to or
`
`from said reflective means;
`
`a diffractive element for diffracting the signal or a portion thereof; and
`
`an arr~y of elements for receiving at least a portion of the signal after it has been diffracted
`
`by said diffi·active element, wherein the at least two ports, the diffractive means and the array
`
`of elements are disposed substantially in the focal plane of said reflective means.
`
`2. A 4-f optical system as defined in claim 1 wherein the array of optical elements are
`
`switches for switching a signal incident thereon from a first direction to another
`
`independence upon a control signal.
`
`3. A 4-f optical system as defined in claim 3, wherein the switches are polarization dependent
`
`switches.
`
`4. A 4-f optical system as defmed in claim 2 wherein the diffractive element is a reflective
`
`diffractive element and wherein the reflective means is a single curved mirror.
`
`5. A 4-f optical system as defined in claim 1 wherein the switch is disposed to receive light
`
`from a second focal plane for selectably switching light received from one of the fust and
`
`second ports to be directed to the other of the first and second ports or back to a same port
`
`from which it originated.
`
`6. A 4-f optical system as defined in claim 1 wherein the array of elements includes a
`
`polarization dependent switch, for reflecting light backwards when the light is of a first
`
`polarization and for switching light to another location when the light is of a second
`
`orthogonal polarization.
`
`0008
`
`7
`
`
`
`7. A 4-f optical system for multiplexing an optical signals comprising:
`
`a first port for transmitting a Gaussian beam of light;
`
`a second port for receiving a demultiplexed beam of light;
`
`a reflective-focusing element for focusing the beam of light received from at least one of the
`
`first and second ports at a first focal plane;
`
`a reflective diffractive optical element at the first focal plane; and,
`
`a switch disposed to receive light from the reflective-focusing element after having been
`
`dispersed in a wavelength dependent manner from the reflective diffractive element for
`
`selectably switching light received from the first to be directed to one of the first second port.
`
`t1i
`
`m
`•:.!
`!d -~
`', j:llt.~
`
`8. A 4-f optical system as defined in claim 7, wherein a diameter of the Gaussian beam at the
`
`first port is substantially the same as a diameter of the beam at the switch, and wherein the
`
`diameter of the Gaussian beam incident upon the diffractive element is substantially less than
`
`the diameter incident upon the switch.
`
`9. A 4-f optical system as defmed in claim 8, wherein the switch is a polarization dependent
`
`switch for switching light of a first polarization in a first direction and for switching light
`
`having a second orthogonal polarization in a second direction.
`
`10. A-4f optical system as defined in any of the preceding claims, wherein the signal
`launched from one of the ports directed to the array of elements is incident upon the
`reflective means at two separate locations, and wherein the reflective means is a single
`curved mirror.
`
`1.
`
`An add/drop comprising:
`two ports with split polarized sub beams each
`focussing elements arranged as a reflective 4f system , see Figure
`1
`a diffraction grating in the first focal plane
`an array of reflective 2x2 switches in the wavelength dispersed
`second focal plane
`two circulators connected to the above mentioned ports for output
`of reflected signals
`
`0009
`
`8
`
`
`
`2.
`
`3.
`4.
`
`5.
`
`6.
`
`7.
`
`8.
`
`9.
`
`10.
`
`11 .
`
`[1] in which polarization splitting at the front end is realized using a
`microlens, a birefringent element, and a half wave plate, see Figures 2a
`and 2b
`[1] in which a single mirror is used as focussing elements, see Figure 3
`[1] in which a diffraction grating is a high efficiency, high dispersion
`diffraction grating
`[1] in which the array of reflective 2x2 switches is realized using a liquid
`crystal array and a pair of polarization beam splitters attached to the
`rear side of the array, see Figure 4a and 4b. The arrangement of Figure
`4b has an additional advantage of low PMD for both add/drop and pass
`through states.
`[1] in which the array of reflective 2x2 switches is realized using a liquid
`crystal array and a birefringent element attached to the front side of the
`array, see Figure 5
`[1] in which there are two devices in one, one being for C and the other
`for L band. Ecah device has its own in/out/add/drop ports that are
`conveniently shifted with respect to each other as to cover the
`respective spectral band. The common optical elements are mirror,
`diffraction grating, and LC array having at least two rows of pixels
`[5] in which the liquid crystal array is twisted nematic liquid crystal
`array
`[8] in which the " ON" state of the liquid crystal is used in "add/drop"
`mode, and " OFF" state of liquid crystal is used in "in/o~t" mode
`[8] in which the inter pixel areas of liquid crystal array are covered by a
`black grid
`[5] or [6] in which the liquid crystal array ·is pi cell array
`
`NOTE: claims for channel equalizer are same except: 1) there is one port, not
`two, and one circulator is connected to that port, and 2) there is no need in
`claim 8. Alternatively, channel equalizer can be realized on the basis of pass(cid:173)
`through state of the above described add/drop module with no circulators.
`
`1::0
`
`I!
`
`0010
`
`9
`
`
`
`D. How does your solution differ from known solutions to the same
`problem?
`Other COADM I channel equalizer devices are based either on waveguide
`or free space optics. The free space optics approaches include diffraction
`grating and MEMS (Lucent), or diffraction grating and LC {). The
`advantages of the present approach over early designs are much smaller
`amount of optical elements, ease of alignment, thermal stability, and high
`channel count.
`
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