Interferometric measurement device

Patent metadata

Field	Value
Publication number	US-9945670-B2
Application number	US-201515121620-A
Country	US
Kind code	B2
Filing date	Feb 26, 2015
Priority date	Feb 26, 2014
Publication date	Apr 17, 2018
Grant date	Apr 17, 2018

Abstract

Interferometric measurement device includes a light source emitting a source signal and optical coupling elements receiving the source signal, directing part of the latter towards a measurement pathway including a Sagnac ring interferometer, of frequency f p , producing a power output signal P OUT polarized according to a first polarization direction, tapping off another part of the source signal towards a compensation pathway producing a return power compensation signal P RET , and directing the output and compensation signals towards detection elements. The compensation pathway includes polarization rotation elements producing the compensation signal according to a second cross-direction of polarization, and optical looping elements redirecting part of the compensation signal towards the measurement pathway; the detection elements include a single detector connected to the coupling elements for receiving the output signal and the compensation signal; the device further includes power equilibration elements equalizing the output power and/or return power are routed towards the detector.

First claim

The invention claimed is:

1. A device ( 100 ; 200 ; 300 ; 400 ) for interferometric measurement of a parameter (Ω R ) to be measured, including:
a wide-spectrum spontaneous-emission light source ( 110 ) emitting a source light signal (S 1,∥ , S′ 1,⊥ ) and having an excess relative intensity noise (RIN),
detection means ( 150 ) delivering an electric signal representative of the result of a measurement of said parameter (Ω R ) to be measured,
electric processing and control means ( 160 ) processing said electric signal to provide said measurement of said parameter (Ω R ) to be measured, and
optical coupling means ( 120 ; 220 ; 320 ; 420 ):
receiving said source light signal (S 1,∥ , S′ 1,⊥ ),
directing a part (S 2,∥ , S′ 2,⊥ ) at least of said source light signal (S 1,∥ , S′ 1,⊥ ) towards a measurement pathway ( 102 ) comprising a measurement interferometer ( 140 ) that includes a phase modulator ( 142 ) and a Sagnac ring ( 141 ), of proper frequency f p , sensitive to said parameter (Ω R ) to be measured, said interferometer receiving, as an input, an input light signal (S IN,∥ ) of input light power (P in ) and producing, as an output, an output light signal (S OUT,∥ ) of output light power (P OUT ) depending on said physical parameter (Ω R ) to be measured and proportional to said input light power (P in ), said output light signal (S OUT,∥ ) being polarized in a first polarization direction and modulated at a modulation frequency f n thanks to said phase modulator ( 142 ),
tapping off another part (S 3,∥ , S′ 3,⊥ ) of said source light signal (S 1,∥ , S′ 1,⊥ ) towards a noise (RIN) compensation pathway ( 103 ) distinct from the said measurement pathway ( 102 ), said compensation pathway ( 103 ) producing a noise (RIN) compensation light signal (S R,⊥ ) having a return light power (P RET ),
directing said output light signal (S OUT,∥ ) and said compensation light signal (S R,⊥ ) towards said detection means ( 150 ),

characterized in that:
said compensation pathway ( 103 ) comprises:
polarization rotation means ( 131 ) adapted to produce said compensation light signal (S R,⊥ ) in a second polarization direction crossed with said first polarization direction, and
means ( 132 ; 134 ; 234 ; 334 ; 434 ) for optically looping said compensation pathway ( 103 ) on said measurement pathway ( 102 ), said optical looping means ( 132 ; 134 ; 234 ; 334 ; 434 ) receiving said compensation light signal (S R,⊥ ) circulating on said compensation pathway ( 103 ) and redirecting a part at least of said compensation light signal (S R,⊥ ) towards said measurement pathway ( 102 ),

said detection means ( 150 ) comprise a single optical radiation detector ( 150 ) connected to said optical coupling means ( 120 ; 220 ; 320 ; 420 ), said optical coupling means ( 120 ; 220 ; 320 ; 420 ) receiving said output light signal (S OUT,∥ ) and said compensation light signal (S R,⊥ ), which circulate on said measurement pathway ( 102 ), for routing them towards said detector ( 150 ),
said device ( 100 ; 200 ; 300 ; 400 ) further includes power balance means ( 132 ; 121 , 133 ; 222 ; 223 ; 233 ; 321 , 333 ; 321 , 322 ; 422 ) correcting said output light power (P OUT ) and/or said return light power (P RET ) routed towards said detector ( 150 ) in such a manner that said return light power (P RET ) is substantially equal to said output light power (P OUT ) at the level of said detector ( 150 ), and
said compensation pathway ( 103 ) has a length adjusted so that said output light signal (S OUT,∥ ) has at the level of the detector ( 150 ) a time delay τ with respect to said compensation light signal (S R,⊥ ) substantially equal to 1/(2*f p ).

2. The interferometric measurement device ( 100 ; 200 ) according to claim 1 , further including a linear polarizer ( 111 ) placed downstream of said light source ( 110 ) to polarize said source light signal (S 1,∥ ) in said first polarization direction.

3. The interferometric measurement device ( 100 ; 200 ) according to claim 2 , wherein said optical coupling means ( 120 ; 220 ) comprise a first four-port two-by-two coupler ( 121 ; 222 ; 233 ).

4. The interferometric measurement device ( 200 ) according to claim 3 , wherein said optical coupling means ( 220 ) comprise an optical circulator ( 221 ) placed upstream of said first coupler ( 222 , 223 ), said optical circulator ( 221 ) having three ports connected to said light source ( 110 ), to one of the ports of said first coupler ( 222 ; 223 ) and to said detector ( 150 ), respectively.

5. The interferometric measurement device ( 100 ) according to claim 4 , wherein said optical looping means comprise a second four-port two-by-two coupler ( 132 ), said power balance means also comprising said second coupler ( 132 ).

6. The interferometric measurement device ( 100 ; 200 ) according to claim 5 , wherein said power balance means comprise an optical attenuator ( 133 ; 233 ) for a light signal (S 3,⊥ ) polarized in said second polarization direction so as to correct said return light power (P RET ).

7. The interferometric measurement device ( 100 ; 200 ) according to claim 4 , wherein said optical looping means comprise a polarization separator ( 134 ; 234 ).

8. The interferometric measurement device ( 100 ; 200 ) according to claim 7 , wherein said power balance means comprise an optical attenuator ( 133 ; 233 ) for a light signal (S 3,⊥ ) polarized in said second polarization direction so as to correct said return light power (P RET ).

9. The interferometric measurement device ( 100 ) according to claim 3 , wherein said optical looping means comprise a second four-port two-by-two coupler ( 132 ), said power balance means also comprising said second coupler ( 132 ).

10. The interferometric measurement device ( 100 ; 200 ) according to claim 9 , wherein said power balance means comprise an optical attenuator ( 133 ; 233 ) for a light signal (S 3,⊥ ) polarized in said second polarization direction so as to correct said return light power (P RET ).

11. The interferometric measurement device ( 100 ; 200 ) according to claim 3 , wherein said optical looping means comprise a polarization separator ( 134 ; 234 ).

12. The interferometric measurement device ( 100 ; 200 ) according to claim 11 , wherein said power balance means comprise an optical attenuator ( 133 ; 233 ) for a light signal (S 3,⊥ ) polarized in said second polarization direction so as to correct said return light power (P RET ).

13. The interferometric measurement device ( 300 ; 400 ) according to claim 1 , designed for a light source ( 110 ) emitting a non-polarized source light signal (S 1,∥ , S′ 1,⊥ ), wherein:
said compensation pathway ( 103 ) comprises an optical isolator ( 332 , 432 ) intended to block a light signal (S′ 2,⊥ ) polarized in the second polarization direction propagating on said compensation pathway ( 103 ) in a reverse direction with respect to said compensation light signal (S R,⊥ ), and
said optical looping means comprise a polarization separator ( 334 ; 434 ).

14. The interferometric measurement device ( 300 ; 400 ) according to claim 13 , wherein said optical coupling means ( 320 ; 420 ) comprise a first four-port two-by-two coupler ( 321 ; 422 ).

15. The interferometric measurement device ( 300 ; 400 ) according to claim 14 , wherein:
said optical coupling means ( 320 ) further comprise a second four-port two-by-two coupler ( 322 ), and
said power balance means comprise said second coupler ( 322 ).

16. The interferometric measurement device ( 300 ; 400 ) according to claim 13 , wherein:
said

Assignees

• Ixblue

Inventors

• Lefevre Herve
• Guattari Frederic
• Molucon Cedric
• Chouvin Stephane

Classifications

• G01C19/727 Primary

  using a passive ring resonator · CPC title

• G01B9/02

  Interferometers · CPC title

• G01B2290/70

  Using polarization in the interferometer · CPC title

• G01C19/726

  Phase nulling gyrometers, i.e. compensating the Sagnac phase shift in a closed loop system · CPC title

• G01C19/722 Primary

  of the mechanical construction · CPC title