United States Patent 55
`6,043,921
`Mar.28, 2000
`[45] Date of Patent:
`Payton
`
`[11] Patent Number:
`
`US006043921A
`
`[54] FADING-FREE OPTICAL PHASE RATE
`RECEIVER
`
`Attorney, Agent, or Firm—Michael J. McGowan;Prithvi C.
`Lall; Michael F. Oglo
`
`[75]
`
`Inventor: Robert M. Payton, Portsmouth, RI.
`
`[57]
`
`ABSTRACT
`
`[73] Assignee: The United States of America as
`represented by the Secretary of the
`Navy, Washington, D.C.
`
`[21] Appl. No.: 08/910,046
`
`[22]
`
`Filed:
`
`Aug. 12, 1997
`
`Tint, C07 oc cceeeescccsssssseececeesnnneeeeees HO4B 10/06
`[SD]
`
`[52] U.S. Ch we
`.... 359/191; 359/156
`[58] Field of Search occ 359/190, 111,
`359/191, 189, 192, 162, 156; 350/349
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`5,140,453
`
`8/1992 Tsushima et al. oe eee 359/192
`
`A method and optical system for fading-free reception of
`optical phase signals having temporally varying
`polarization, phase and phase frequency is provided. Two
`orthogonally polarized local oscillators light waves of dif-
`ferent frequencies are utilized to produce optical interfer-
`ence with an unknownpolarization state optical input signal.
`Square law detection of the resultant optical interference
`yields a composite radio frequency signal which is decoded
`into four electronic outputs. These outputs are temporally
`differentiated and cross multiplied to produce a single com-
`posite output corresponding to the phase rate of the optical
`input signal. The total power of the four electronic outputs
`is proportional to the input signal power. The present inven-
`tion thus maintains constant signal to noise ratios and avoids
`the use of internal clippers and limiters.
`
`Primary Examiner—Kinfe-Michael Negash
`
`15 Claims, 8 Drawing Sheets
`
`500.
`
`(S P L M)
`
`400.
`
`(Y-P 0 M)
`
`999
`
`
`600
`;
`1900
`700
`
`HALLIBURTON, Exh. 1011, p. 0001
`
`HALLIBURTON, Exh. 1011, p. 0001
`
`

`

`U.S. Patent
`
`Mar.28, 2000
`
`Sheet 1 of 8
`
`6,043,921
`
`Generate X linear
`polarized light
`beam
`
`Generate Y linear
`polarized light
`beam
`
`103
`106
`
`Phase lock X and Y polarized light
`beam sources
`
`105
`
`109
`
`Form Composite Beam from X and Y
`beams
`
`112
`
`Receive external signal
`
`115
`
`Form Composite Beam with external
`signal
`
`118
`
`Convert optical signal to electrical
`signal
`
`121
`
`Decode electrical signal
`
`124
`
`Differentiate and Cross Multiply
`Decoded Values
`
`FIG.
`
`1
`
`HALLIBURTON, Exh. 1011, p. 0002
`
`HALLIBURTON, Exh. 1011, p. 0002
`
`

`

`U.S. Patent
`
`Mar.28, 2000
`
`Sheet 2 of 8
`
`6,043,921
`
`(NOd-A)°00F (NIdS)
`
`666
`
`‘00S
`
`HALLIBURTON, Exh. 1011, p. 0003
`
`HALLIBURTON, Exh. 1011, p. 0003
`
`

`

`6,043,921
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`oD)
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`fry
`
`U.S. Patent
`
`Mar.28, 2000
`
`Sheet 3 of 8
`
`300
`
`nh
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`mM
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`°
`m
`oO
`
`395Lo
`
`||‘
`
`393
`
`HALLIBURTON, Exh. 1011, p. 0004
`
`HALLIBURTON, Exh. 1011, p. 0004
`
`

`

`U.S. Patent
`
`Mar.28, 2000
`
`Sheet 4 of 8
`
`6,043,921
`
`(Ss@0)‘Ler
`vOl
`
`(S@0)Ger
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`STO
`
`HALLIBURTON, Exh. 1011, p. 0005
`
`HALLIBURTON, Exh. 1011, p. 0005
`
`

`

`U.S. Patent
`
`Mar.28, 2000
`
`Sheet 5 of 8
`
`6,043,921
`
`nz
`
`500
`
`FIG.
`
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`HALLIBURTON, Exh. 1011, p. 0006
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`HALLIBURTON, Exh. 1011, p. 0006
`
`

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`6,043,921
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`Mar.28, 2000
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`Sheet 6 of 8
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`U.S. Patent
`
`
`
`HALLIBURTON, Exh. 1011, p. 0007
`
`HALLIBURTON, Exh. 1011, p. 0007
`
`

`

`U.S. Patent
`
`Mar.28, 2000
`
`Sheet 7 of 8
`
`6,043,921
`
`08d
`
`908
`
`608
`
`664
`
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`£08
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`004
`
`HALLIBURTON, Exh. 1011, p. 0008
`
`HALLIBURTON, Exh. 1011, p. 0008
`
`

`

`U.S. Patent
`
`Mar.28, 2000
`
`Sheet 8 of 8
`
`666|+E26|6r6/696!GLav!|oSC&6S16|;~908|(<<)
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`6,043,921
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`HALLIBURTON, Exh. 1011, p. 0009
`
`HALLIBURTON, Exh. 1011, p. 0009
`
`

`

`Accordingly, it is an object of the present invention to
`provide a method for demodulating the phase information
`from a coherent optical signal having temporal changes in
`phase and polarization.
`It is a further object to provide an electro-optical system
`for phase and polarization fading-free reception of optical
`phase signals.
`Astill further object of the present invention is to provide
`reception of optical phase signals without clipping or lim-
`iting the output electronic voltages resulting from reception
`of the optical signal.
`Yet another object of the inventionis to provide a receiver
`output signal to noise ratio which is constant and non-
`temporally varying.
`In accordance with these and other objects, the invention
`is, a method and optical device for providing fading-free,
`constant signal
`to noise ratio reception of optical phase
`signals having polarization and phase variations. The
`method includes (1) generating separate X and Y-polarized
`reference local oscillator light waves, each having a discrete
`frequency, (2) phase locking the two local oscillator light
`waves so that their polarizations are orthogonal to each
`other, (3) forming a composite local oscillator light wave by
`combining the two orthogonal local oscillator light waves,
`(4) receiving an external optical signal; (5) forming a new
`composite signal by combining the external signal with the
`phase-locked composite local oscillator; (6) converting the
`new composite signal to an equivalent electrical signal; (7)
`Coherent optical receivers, on the other hand, remedy
`decoding the equivalent electrical signal into component
`many of the problems of the earlier incoherent receivers.
`voltages; and (8) temporally differentiating and cross mul-
`Typically, coherent optical receivers combine the input
`tiplying the component voltages to generate a phase rate
`optical signal with a signal produced byalocal oscillator to
`form an interference. The interference between the two
`output.
`The optical device is comprised of a heterodyne optical
`receiver with two coherent
`local
`light sources (such as
`highly coherent, phase locked lasers). It receives an external
`optical signal and forms an interference between the two
`local light sources and the external signal. Photodetectors
`are used to convert this optical interference into an elec-
`tronic radio-frequency wave which can then be decoded into
`four outputs which fully describe the phase and polarization
`of the external optical signal. The four outputs are tempo-
`rally differentiated and cross multiplied resulting in an
`output which is a linear combination of the phase rate and
`the signal polarization rotational angle.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`1
`FADING-FREE OPTICAL PHASE RATE
`RECEIVER
`
`STATEMENT OF GOVERNMENT INTEREST
`
`The invention described herein may be manufactured and
`used by or for the Government of the United States of
`America for Governmental purposes without the payment of
`any royalties thereon or therefor.
`BACKGROUND OF THE INVENTION
`
`(1) Field of the Invention
`The present invention relates generally to optical phase
`signal reception. In particular, a method and device for
`reception of a polarization and phase varying optical phase
`signal without output power fade is provided.
`(2) Description of the Prior Art
`Devices for the reception of optical signals are well
`knownin the prior art. Included in the prior art are devices
`which use photodetectors to provide an electric output signal
`proportional to the incident optical signal power. In many of
`these devices, fading due to variations in phase and polar-
`ization is avoided by incoherent optical detection. However,
`the elimination of polarization fading by incoherent detec-
`tion comesat a cost. First, the strength of the output signal
`varies as the square of the input signal power. This variation
`means that for every decibel of input signal power lost in a
`receiver system, two decibels of receiver output current are
`lost. This square law characteristic has limited incoherent
`optical receivers in the prior art to dynamic ranges of less
`than 80 dB and optical detection noise floors to greater than
`-80 dBm (dB referenced to 1 milliwatt) per Hertz band-
`width. Moreover, the phase characteristics of the incident
`optical signal cannot be determined by this type of optical
`receiver.
`
`optical waves produces an optical “beat” which can be used
`to measure the phase difference between the signal and the
`local oscillator. This “beat” is as a result of the square law
`nature of the optical detectors. The earliest coherent optical
`receivers, known in the art as homodyne. receivers, use a
`local oscillator with the same frequency as the input optical
`signal. This method allows the detection of the phase
`characteristics of the incoming signal; however, the output
`signal is subject to fading caused by either the phase or the
`polarity of the input signal. Later, heterodyne receivers were
`developed which used a local oscillator with a frequency
`different from that of the incomingsignal to eliminate fading
`due to phase. Nevertheless, fading, due to polarization,
`remains a problem in theart.
`Prior art phase detectors have relied upon the capabilities
`of the underlying optical receiver. These phase demodula-
`tion oriented optical receivers have historically been limited
`in two ways. First, the inability of the prior art to produce a
`phase and polarization fading-free receptor has caused the
`performance of prior art phase detectors to be sensitive to
`variations in phase and polarization of the input optical
`signal.
`Additionally, prior art efforts have required constant out-
`put powerto input powerratios—inorderto achievethis,the
`output voltage is normally clipped or otherwise electroni-
`cally limited. The use of these clippersor limiters in the prior
`art causes signal to noise ratios in the detector to vary over
`time.
`
`6,043,921
`
`2
`Noprior art methodsor devices exist which provide phase
`and polarization fading-free demodulation of phase infor-
`mation while maintaining a constant, nontemporally-
`varying signal to noise ratio.
`SUMMARYOF THE INVENTION
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`The foregoing objects and other advantagesof the present
`invention will be more fully understood from the following
`detailed description and reference to the appended drawings
`wherein:
`
`FIG. 1 is a process flow chart for the method of providing
`polarization and phase fading-free reception of optical phase
`signals;
`FIG. 2 is a high level block diagram of one embodiment
`of the apparatus for polarization and phase fading-free
`reception of optical phase signals;
`FIG. 3 is a component
`level view of the linearly
`X-polarized local oscillator module;
`FIG. 4 is a component
`level view of the linearly
`Y-polarized local oscillator module;
`
`HALLIBURTON, Exh. 1011, p. 0010
`
`HALLIBURTON, Exh. 1011, p. 0010
`
`

`

`6,043,921
`
`3
`FIG. 5 is a componentlevel view of the local oscillator
`phase locking module;
`FIG. 6 is a component level view of the optical signal
`receptor module;
`FIG. 7 is a componentlevel view of the signal decoding
`module; and
`FIG. 8 is a componentlevel view of the differentiation and
`cross multiplication module.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`Referring now to the drawings, and in particular to FIG.
`1, a process flow chart for the method of providing polarity
`and phase fading-free reception of optical phase signals is
`shown. In order to mathematically quantify the limitations
`and operation of the method, several wave equations are
`used in the specification. The following table lists the names
`of the variables and a brief description of their use in the
`wave equations.
`
`E:xrys
`
`OLLys
`
`AOxyxy
`
`®8xrys
`
`YWixLy,s
`
`9Lx,Lys
`
`Absxy
`
`Pixys
`
`PLxs,Lys,1
`
`Vixwys
`
`The wave amplitude of each of
`the optical signals LX =
`linearly X-polarized light wave
`LY = linarly Y-polarized light wave
`S = external optical signal
`The wave radian frequency of
`the optical signals; the
`frequencies of the linear X and
`the linear Y-polarized light
`beamsare not equal to each
`other or the frequency of the
`external optical signal.
`The difference between the wave
`radian frequencies
`A@y = Ws - Opy
`AOx = Og -— OLX
`AOxy = Ox - Oy
`The spatial rotational angle of
`the optical signals, these are
`constant for the linearly X and
`Y-polarized light waves:
`
`Oxy
`‘LX =
`
`=0 Oyan
`We 5
`
`Theellipticity angle of the
`optical signals, these are also
`constant for the linearly X and
`Y-polarized light waves:
`Yix =9
`Ypy =0
`Pry = 0
`The temporal phase of the
`optical signals
`Theoffset of the linearly
`polarized signals phase from
`that of the incoming signal:
`Adx. = %s - OLx
`Ady = s - Pry
`Theelectrical powerof the
`optical signals
`Theelectrical powerof the
`interferences, Prxg is the
`interference between the
`linearly X-polarized local light
`wave and the external optical
`signal, Pry between the linearly
`Y-polarized local light wave and
`external optical signal, and
`Pixry between the two linearly
`polarized local light waves
`The voltage output from a
`photoreceiver upon reception of
`the local oscillator light waves
`and the external optical signal
`
`4
`
`-continued
`
`
`
`The voltage output from a
`photoreceptor due to
`interference between the two
`inearly polarized local
`oscillator light waves and the
`external optical signal
`The impedance of the
`ransmission media the optical
`signals propagate through
`Theresistance loading the
`photodetector
`The responsitivity of the
`photodetector
`The amplification of the input
`signal
`The amplification of the
`inearly X and Y-polarized
`signals
`Time; for temporally varying
`variables
`
`VLxs,Lys,1
`
`n
`
`Ry
`
`R
`
`A
`
`Axy
`
`t
`
`In FIG. 1, the process for receiving a temporally varying
`frequency, phase and polarization optical phase signal with
`a constant signal to noise ratio is illustrated. In particular, in
`step 103, a local oscillator is used to generate a first distinct
`frequency light wave linearly polarized in the X direction
`and mathematically described as:
`
`—
`Erx=
`
`Exx cos(wiyt + bry)
`6
`
`Wd)
`
`In step 105, a second local oscillator is used to generate a
`second distinct frequency linearly Y-polarized light wave,
`which is mathematically described as:
`
`EpyO=
`
`0
`Ezy cos(wpyt + bry)
`
`(2)
`
`The two light waves are used in step 106 to phase lock the
`local oscillators. In particular, the radian frequencies and
`phases of the two phase locked spatially orthogonal optical
`local oscillator signals comprise a set of component light
`waves which are compared to each other. The local oscil-
`lators are adjusted until the relation
`
`Oyy-@, y-ADWyy
`
`(3)
`
`the radian frequencies of both
`In this way,
`holds true.
`oscillators are held such that each significantly exceeds the
`bandwidth of the incoming optical signal.
`These two optical signals are then combined into a
`composite optical signal in step 109. The heterodyne cross
`interference of these two signals is zero because they have
`orthogonal polarization, thus:
`
`_
`ARLR
`vexzy(2) = rr ()- Ezy (Q) = 0
`
`(4)
`
`In step 112, the incident optical signal is received. Since
`the optical signal is arbitrary, it has unknown, and possibly
`temporally variant values for the wave amplitude E,, the
`rotational angle of the wave temporally 0, phase,,
`the
`ellipticity angle Ws , and the wave radian frequency W..
`Further,
`the incident optical signal
`is mathematically
`described as:
`
`HALLIBURTON, Exh. 1011, p. 0011
`
`10
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`HALLIBURTON, Exh. 1011, p. 0011
`
`

`

`5
`
`Es@=
`
`6,043,921
`
`(6)
`
`cos(Wst)
`8 —sin(@s) | 0 sn| snus
`cos(ps)
`|
`|
`
`
`
`FE sin(9s)|[cos(s)cos(As) 0 cos(ds) —sin(¢s)
`
`sin(st)
`
`15
`
`vzxs(t) =
`
`
`ARR
`
`Exx Es (d[cos(9s cos(Ws cos(Awyt + Ady) +
`sin(Os)sin(Yis)sin(Awyt + Ady)]
`
`(11)
`
`Dueto the orthogonal nature of the local oscillator signals,
`This incident signal is combined with the composite optical
`the cross interference between them Vizx7yis zero. Thefinal
`signal formed in step 109 to form a composite input optical
`10
`two terms of the photoreceptor output represent the cross
`signal in step 115. The resultant signal is converted to an
`interference between the incident signal and the two local
`electrical signal by a photoreceiver in step 118. The output
`oscillator signals. These terms are described mathematically
`from the photoreceiver is a linear combination of several
`as:
`electrical power values as described in the following equa-
`tion:
`
`You = ARLR(PLx () + Pry (OD + Ps(t) + Pixs (+ Prys()+ Prxty(D)
`
`(6)
`
`or equivalently, in terms of the photoreceptor output volt- 20
`ages:
`
`
`A
`A
`A
`_ ARR E
`“uys(0 =
`ty Es(0)[-sin(@scostscos(Aiwyt+ Ady) +
`cos(@s sin(Ws sin(Awy rt + Ady )]
`
`(12)
`
`(7) vs or alternatively, using optical power termsas:
`vouxViOVOxslt+Yvoltelt)
`In particular, the baseband homodyneself-interference out-
`vixs(1) = 2ARLRYPry Ps(0) [eos(0s)cos(WsJoos(Awy t + Ady) +
`puts are:
`sin(@s )sin(Ws )sin(Awy + Ady )]
`
`14
`-
`i
`d4)
`viys(t) = 2ARLRYPryPs(1) [-sinl@sJoosJoost + Ady)+
`8)
`AR,RE?y
`-
`ARR
`
`
`AR
`AR,RE?
`(9)
`.
`
`vy (t) = ARRoe (t)-Ery ®) =ARRELy_ ARLRPy In step 121, the photoreceptor output is demodulated and
`7
`decoded into four further outputs: Vy, Vo, Vyp and Vyo.
`These four outputs are described mathematically as:
`
`vzx (ft) = ee (1): Exx (Q)) =—~—— = ARLRPLx 30 costssin(Ws)sin(Awyr + Ady)]
`
`(13)
`
`vp (0) = (Your (Neos(Aw,t))
`
`.
`VxQ (t) = (Your (2)sin(Aw,t))
`
`
`AxARR
`
`
`AxARLR
`
`:
`:
`.
`Ezy Es (t)[cos@s cos(Ws cos(Ady ) + sin(@s sins )sin(A¢x )]
`
`.
`.
`.
`Exx Es (O[sin(@s sins Jcos(Ady ) — cos(s Jcos(Ws )sin(Adx )]
`
`vy (0) = (Your (Neos(Aw,t))
`
`
`AyARLR
`
`:
`:
`.
`Ezy Es(0)[—sin@s )cosWs Jcos(Ady cos(Os)sin(Ws sin(Ady )]
`
`=
`
`(Vou
`
`(t)sin(Aw
`
`yt))Ay AR
`
`NNByEs(0)[cos(9ssins)eos(Ady) + sin(@seos(ys)sin(Ady)]
`
`or alternatively, in terms of optical power:
`
`vyr(0) = Ay ARLRV Pry Ps() [cos(@s oos(is cosAdy) + sins sin(s)sinAgy)]
`
`vy9 (0 = AyARLRVPx Ps(0) [sin(@s)sin('scos(Apy ) + cos(sJoos(iis)sin(Ady )]
`
`vy(t) = Ay ARLRYPryPs(0) [-sin(@s cos(s )cos(Ady) + cos(9s)sin(Ws)sin(Ady)}
`
`vyo(t) = Ay ARLRYVPryPs[cosssinscos(Apy) + sins)cos(Ys)sin(Ady)]
`
`(15)
`
`(16)
`
`ay
`
`18
`
`”
`
`1%
`
`20)
`
`PD)
`
`(2)
`
`-continued
`
`=
`ARR _
`vs) = GyEsEs) =
`
`
`AR,RE?
`
`= ARLRPs(n)
`
`(10)
`
`65
`
`Since Ay and Ay are selected (during steps 103 and 105)
`whenthe local oscillator signals are generated such that:
`
`HALLIBURTON, Exh. 1011, p. 0012
`
`HALLIBURTON, Exh. 1011, p. 0012
`
`

`

`6,043,921
`
`(23)
`
`8
`long as the powerof the external optical signal is non-zero,
`the output power from the decoding step 121 is non-zero,
`effectively eliminating fade due to changesin polarization,
`phase or frequency.
`
`a coefficient based on this relationship and the common
`multipliers in the output voltages can be derived as follows:
`
`Ho
`
`=
`
`
`AyAR,R
`AyARLR
`LX =
`AXARLE
`|,
`Dy
`2n
`
`E,
`LY
`
`QA)
`
`The four equations for the outputs from the photoreceptor
`can thus be simplified as follows:
`
`Finally, in step 124, the output voltages from decoding
`step 121 are differentiated and cross multiplied to generate
`a single output whichis a linear combination of the external
`optical signal’s phase rate and polarization rotational angle.
`
`In order to generate the synthesized phase rate output, the
`four outputs from decoding step 121 are first temporally
`differentiated, thus:
`
`10
`
`15
`
`30)
`“
`
`31
`e
`
`(32)
`
`33,
`“
`
`d
`+Molcos(,)coslWs)cos(Ad,) + sin(G,)sin(W.)sin(Ad,)] PES@
`d
`+ HoEs(D[-cos@,)cos(y,)sin(Ad,) + sin(@,)sin(W)cosAgy)] 7 Ad,
`+MoEs()[-sin@,)cos(,cos(Ad,) + cos(9,)sinWW,sing,)] “0,t
`d
`+HoE.()[—cos@,)sin(Ws)cos(Ad,) + sin(@,cos,)sin(Ag,)] ats
`d
`+olsin@,)sin(W,)cos(Ag,) — cos(@,cos(,)sin(Ag,)] ahEs)
`d
`+HoE.(N[-sin@,)sin(,)sin(Ag,) — cos(0;)cosWs)cosAdy)] 7 Ag,
`d
`+MoE(1[cos@,)sin(ys)cos(Ag,) + sin(@s)cos(,)sin(Ad,)] as
`d
`+ MoE. (sin,Jcos(Ws)cos(Ag,) + cosG,)sin(ys)sin(Ag,)] 7 bs
`d
`+o[-sin@,)cos(W,)cos(Ady ) + cos(@,)sin(W,)sinAdy )] 7 Es
`d
`+HoE.(N[sin(@,)cos(y,)sin(Ady ) + cos(@,)sin(Ws)cos(A¢y)] afte
`d
`+ HoE,(t)[—cos@scos(, Jcos(Ady ) — sin(@,)sin(y,sin(Ady)] —4,dt
`d
`+HMoE.(f[sin@,)sin(W,)cos(A¢y) + cos(@,)cos(Ws)sin(Ady )] F bs
`d
`+Molcos(@,)sinWs)cos(Ady) + din(@s)cosWs)sin(Ady)] PEs)
`d
`+HoE.([—cos@,)sin(,)sin(Ady) + sin(@,costs)cos(Ady )] 7 Ady
`d
`+HMoE.([-sin@,)sin(,cosAdy ) + cos(@scosts)sin(Adgy)] ah ast
`d
`+ MoEs(O[cos(O,cos.)cos(Ady ) — sin(@,)sin(Ws)sin(Ady )] 7 bs
`
`ay
`dt xt =
`
`ay
`dre
`
`=
`
`d a
`
`d a
`
`ne
`
`vxr(t) = MoE (1)[cos(@s \cos(Ws Jcos(Agy ) + sin(Os )sin(ys sin(Agy )]_
`
`vxo(t) = HoEs (o)[sin(Os )sin(ys cos(Agy ) — cos(Os cos(Ws )sin(Ady )]
`
`vyr(t) = HoEs([—sin@s Jcos(Ws Jcos(Ady ) + cos(@s )sin(Ws Jsin(Ady )]
`
`vyglt) = MoEs (D[cos@s sins Jcos(Ady) + sin(@s costs Jsin(Ady )]
`
`(25)
`
`(26)
`
`(27)
`
`(28)
`
`The sum of the power of these four outputs, that is:
`(29)
`P=V,PO+Ve9O+Vv7(O+Vv9(O=HoE.(D=2MHoPO
`is stabilized so that
`the instantaneous poweris directly
`proportional to the powerof the external optical signal. As
`
`55
`
`60
`
`65
`
`The terms are then combined into two differentiated and
`
`cross multiplied voltages, corresponding to the linearly X
`and Y-polarized inputs which generated them:
`
`d
`d
`Vxpcu = Vxo ww —Vur 4 (M2)
`
`d
`d
`Vypcm = Vo 7 We) — Vi 5 xn)
`
`(34)
`
`(35)
`
`HALLIBURTON, Exh. 1011, p. 0013
`
`HALLIBURTON, Exh. 1011, p. 0013
`
`

`

`6,043,921
`
`Substitution yields:
`
`Vepem = WOE?(2)
`
`2
`2
`Vyocm = MoES
`
`[cos*(0,Joos?(Ws) + sin’(W)] =a6, +
`d
`‘
`d
`—cosly’s)sin(s) = 8s — cos(O.)sim(Os) Ws
`d
`[cos”(,)sin?(W,) + sin?(@,)cos?(W.)] —Ady +
`dt
`d
`d
`— cos,)sin(Ws)— 8, — cos, sin(s)—— Ws
`dt
`dt
`
`69)
`
`37
`ald
`
`These two component electronic signals can then be
`combined to generate a polarization fading-free phase rate
`signal Vinca
`
`d
`d
`Vocu (0 = Vo 5 Yu) “Wy 7? + Vxo 7 - Ve 7G WVxo) =
`Vypcu + Vxpcm
`
`vo)
`4
`_
`dd
`Vocu (1) = MoEs |a6 - 2oost,sin)<6.)
`dt
`dt
`r2,.|
`&
`.
`d
`Vocm (1) = HOES |a6 - sin24)(0)
`
`(38)
`
`(39)
`
`(40)
`
`If the signal polarization angle (6,) is temporally constant,
`then the synthesized output signal (Vp¢,q,) Will contain only
`the phaserate. If the rotational angle varies, then the system
`output signal will contain a polarization noise component.
`However, because the noise component is additive, many
`signal processing methods exist for handling this type of
`noise condition.
`is
`it
`Before discussing various figures (FIGS. 2-6),
`instructive to note various blocks therein are designated by
`respective designated numerals and respective descriptors
`obtained by using capital
`letter for each word in each
`descriptor.
`Referring now to FIG. 2, one embodimentofthe optical
`device implementing the present
`invention’s method for
`phase and polarization fading-free reception is shown. The
`device consists of X-polarized local oscillator lightwave
`generating module 300 (also designated as “OM7”),
`Y-polarized local oscillator lightwave generating module
`400 (also designated as “Y-POM”), local oscillator signal
`phase locking module 500 (also designated as “SPLM”),
`incoming optical receiver module 600 (also designated as
`“IORM”), electronic decoding module 700 (also designated
`as “EDM”), electronic radio-frequency oscillator 800 (also
`designated as “ERFM”), and differentiation and cross mul-
`tiplication module 900 (also designated as “DACMM”).
`Coherent light source 303 (also designated as “CLS”)
`generates linearly Y-polarized light beam 391. Light beam
`391 passes through optics 330 (also designated as “OS”) and
`formslight beam 394. At the sametime, linearly Y-polarized
`light beam 491 is also generated by coherent light source
`403 (also designated as “CLS”) and passes through optics
`430, forming light beam 494.
`Resulting light beams 394 and 494, both linearly polar-
`ized in the Y direction from optics 330 and 430 (also
`designated as “OS”), are directed into optics 510. Optics 510
`combines the two signals into one interference which is
`detected and converted into electrical signals carried by
`wires 521 and 524 into phase locking electronics 550 (also
`designated as “PLE”). Phase locking electronics 550 com-
`pares the phase and polarization of the resulting interference
`and adjusts the phase and polarization characteristics of
`coherent
`light sources 303 and 403 (also designated as
`
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`“CLS”) through control channels 301 and 401 setting the
`phase relationship such that the difference in phase between
`the two signals is exactly the same as the phase of the
`reference radio frequency oscillator 800 (also designated as
`“ERFM”) and is also locked close to the frequency of the
`incoming optical signal.
`Linearly Y-polarized light beam 391 is also rotated by
`optics 330 (also designated as “OS”)
`forming linearly
`X-polarized light beam 396. Linearly X-polarized beam 396
`and linearly Y-polarized light beam 495 are propagated from
`optics 330 and 430 into optics 610 (also designated as
`“OS”), where they are combined to form local composite
`light beam 691. Optical receiver module 650 (also desig-
`nated as “ORM”) combines local composite light beam 691
`with external optical signal 1900 to form a composite optical
`beam. The composite optical beam is interfered and con-
`verted into a single channel electronic radio frequency signal
`which is carried across wire 683 to electronic decoding
`module 700 (also designated as “EON”). There, the channel
`is broken into four separate stabilized voltage output chan-
`nels 803, 806, 809, and 812 which represent Vx7, Veo, Ven
`and Vy.
`Voltage output channels 803, 806, 809, and 812 connect
`to differentiation and cross multiplication module 900 which
`temporally differentiates the voltages and combines them to
`yield synthesized phase rate output 999. Synthesized phase
`rate output 999 corresponds to (Vpeqy)-
`Referring now to FIG. 3, a component level view of the
`X-polarized signal generating module 300 is presented.
`Coherent light source 303 (also designated as “CLS”) gen-
`erates linearly Y-polarized light beam 391 with an electric
`field magnitude larger than E,y and radian frequency of w,y.
`Light beam 391 propagates from coherent light source 303
`into a non-polarized optical beam splitter 333 (also desig-
`nated as “N-POBS”). The light beam is split
`into two
`fractional light beams 392 and 393. Fractional light beam
`392 is propagated to optical power meter 335 (also desig-
`nated as “OPM”), Optical power meter 335 monitors the
`power of the optical signal generated by coherent
`light
`source 303 and ensures that the amplitude is held stable.
`Fractional light beam 393 passes into optical beam splitter
`337 (also designated as “OBS”). Fractional light beam 393
`is split into two portions; light beam 394 propagates from
`optical beam splitter 337 into local signal phase locking
`module 500 while light beam 395 propagates into polariza-
`tion rotation device 339. Polarization rotation device 339
`
`rotates linearly Y-polarized light beam 395 into linearly
`X-polarized light beam 396. Linearly X-polarized light
`beam 396 then propagates into incoming receptor module
`600 (also designated as “IORM”).
`Referring now to FIG. 4, a component level view of the
`Y-polarized signal generating module 400 is presented.
`Coherent light source 403 (also designated as “CLS”) gen-
`erates linearly Y-polarized light beam 491 with an electric
`field magnitude larger than E,,, and radian frequencyof w,y.
`Light beam 491 propagates from coherent light source 403
`into optical beam splitter 433 (also designated as “OBS”).
`Light beam 491 is split into two fractions. Fractional light
`beam 492 is propagated to optical power meter 435 (also
`designated as “OPM”). Optical power meter 435 monitors
`the powerof the optical signal generated by coherentlight
`source 403 and ensures that the amplitude is stable. Frac-
`tional light beam 493 passes from optical beam splitter 433
`into optical beam splitter 437 (also designated as “OBS”).
`Fractional light beam 493 is split into two portions; light
`beam 494 propagates from optical beam splitter 437 into
`local signal phase locking module 500 while light beam 495
`propagates into incoming receiver module 600.
`
`HALLIBURTON, Exh. 1011, p. 0014
`
`HALLIBURTON, Exh. 1011, p. 0014
`
`

`

`6,043,921
`
`11
`Referring now to FIG. 5, a componentlevel view of local
`signal phase locking module 500 (also designated as
`“LSPLM”)is presented. Incoming linearly Y-polarizedlight
`beams 394 and 494 propagate into optical beam splitter 513
`(also designated as “OBS”) from X-polarized signal gener-
`ating module 300 and Y-polarized signal generating module
`400. Optical beam splitter 513 divides light beams 394 and
`494 into half, with approximately half of the power of each
`propagating on in light beams 591 and 592. Light beams 591
`and 592 contain Y-polarized light of two different
`frequencies, corresponding to the frequencies of light gen-
`erated in X-polarized light oscillator generating module 300
`and Y-polarized local oscillator generating module 400.
`Light beams 591 and 592 strike photodetectors 516 and 519
`(also designated as “PD”). Photodetectors 516 and 519 are
`closely matched in responsivity. The output from photode-
`tectors 516 and 519 are carried over wires; 521 and 524 to
`intersection node 553. At intersection node 553, the current
`generated by photodetectors 516 and 519 is subtracted,
`yielding a difference in current
`that
`is sunk into radio
`frequency amplifier 556. Radio frequency amplifier 556
`generates an electrical voltage wave which has a radian
`frequency equal to the difference between the frequencies of
`light beams 394 and 494. This voltage wave is carried by
`wire 558 to phase-locked loop electronics 559 (also desig-
`nated as “PLLE”). Phase-locked loop electronics 559 mea-
`sures the frequency and phase of light beams 394 and 494
`and comparesit against the reference frequency from elec-
`tronic radio frequency oscillator 800 in order to control the
`beat frequency and phase of the coherent light sources.
`Referring now to FIG. 6, a component level view of
`incoming receptor module 600 is presented. Linearly
`X-polarized light beam 396 and linearly Y-polarized light
`beam 495 propagate into optical beam splitter 613 (also
`designated as “OBS”). Optical beam splitter 613 divides
`light beams 396 and 495 into local composite light beams
`691 and 694. Local composite light beam 694 propagates to
`optical power meter 621 (also designated as “OPM”). Opti-
`cal power meter 621 measures the sum of the power of the
`two orthogonally polarized light beams 396 and 495. By
`checking the electrical output at the radian beat frequency
`,s-W,-, the system is able to verify that both light beams
`are present and are orthogonally aligned.
`Local composite light beam 691 propagates to optical
`beam splitter 615 (also designated as “OBS”). External
`optical signal 1900 is also directed into optical beam splitter
`615. Optical beam splitter 615 forms a composite beam
`comprised of external optical signal 1900,
`linearly
`X-polarized light beam 495, and linearly Y-polarized light
`beam 396, and then splits the formed composite beam
`precisely in half into composite beams 692 and 693. Com-
`posite beams 692 and 693 thus comprise light of three
`frequencies and polarizations: @, radian frequency and
`arbitrary unknown polarization from the external source,
`®,y radian frequency and linear X-polarization from light
`beam 396, and w,, radian frequency and linear
`Y-polarization from light beam 495. Composite beams 692
`and 693 strike photodetectors 617 and 619 (also designated
`as “PD”). Photodetectors 617 and 619 generate current in
`proportion to the power of the composite beams which is
`passed through wires 681 and 682 to intersection node 623.
`At intersection node 623,
`the two currents generated by
`photodetectors 617 and 619 are subtracted and the difference
`is sunk into the input impedanceof radio-frequency ampli-
`fier 633 (also designated as “RFA”) thereby developing a
`voltage which is amplified and placed on wire 683. This
`voltage is a composite radio frequency wave which has two
`
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`
`12
`components centered at radian frequencies w,—w,y and
`®,-W,y. These two frequencies correspond to the beat
`frequencies between linearly Y-polarized light beam 396 and
`external optical signal 1900 (,—«,,,) and between linearly
`X-polarized light beam 495 and external optical signal 1900
`(Q;-,y) indicate the difference in frequency between the
`respective optical sources. Furthermore, the magnitude and
`phase of the components of this composite radio frequency
`wave provide the four pieces of information required to
`resolve the phase rate of external optical signal 1900.
`Referring now to FIG. 7, a component level view of the
`decoder or an electronic decoding module 700 is shown.
`Wire 683 carries a composite radio frequency signal
`to
`powersplitter 703. Power splitter 703 (also designated as
`“RFPS”) divides the input RF signal power equally onto
`wires’ 781 and 782. Wires 781 and 782 carry the diminished
`signal to amplifiers 706 (also designated as “A”) and 730
`(also designated as “A”) which amplify the signal. The
`amplified signals are carried by wires 783 and 784 to power
`splitters 709 (also designated as “PS”) and 733. Power
`splitters 709 and 733 (also designated as “PS”) divide the
`signal into four channels on wires 785, 786, 787, and 788.
`Simultaneously, two reference inputs are developed. In
`particular, a reference RF wave of radian frequency Aw, is
`input on wire 780 to amplifier 721 (also designated as “A”).
`Amplifier 721 boosts the signal and then passesit a