| 摘要 |
A fiber-optic measurement device (10) includes a SAGNAC ring interferometer (20) having a proper frequency fp. The aim is to improve response time while maintaining high precision across the measurement range. Biasing elements (130) are used to produce: a first biasing phase-differential modulation component Δφb1(t) (34) which is periodic in time-slots, having levels +π and −π, at a first biasing modulation frequency fb1 such that fb1=(2k1+1) fp, k1 being a natural number; and a second periodic biasing phase-differential modulation component Δφb2(t) (35), having extreme amplitudes +π/a and −π/a, a being a non-zero real number such that |a|>1, at a second biasing modulation frequency fb2 such that fb2=(2k2+1) fp, k2 being a non-zero natural number such that k2>k1. A gyrometer including such a measurement device and a navigation or inertial-stabilization system including at least one such gyrometer are also described. |
| 主权项 |
1. A fiber-optic measurement device (10) of the type in which a parameter to be measured generates a phase difference Δφp between two counter-propagating waves (24, 25), including:
a light source (11), a fiber-optic SAGNAC ring interferometer (20), preferably single-mode, including a coil (21) and a splitting element (23), in which said two counter-propagating waves (24, 25) propagate, said ring interferometer (20) having a proper frequency fp, an electromagnetic radiation detector (14), receiving the luminous power (37) exiting from said ring interferometer (20) and delivering a modulated electrical signal (38) representative of the luminous power (37), which is function of the total phase difference Δφt between said two counter-propagating waves (24, 25) at the output of said ring interferometer (20), a modulation chain (30) adapted to modulate said luminous power (37) exiting from said ring interferometer (20), said modulation chain (30) including:
at least one digital/analog converter (31) adapted to process a digital control signal to deliver an analog control signal,an amplifier (32) adapted to process said analog control signal to deliver a modulation control voltage Vm(t),at least one phase modulator (33) placed in said interferometer (20), which, when subjected at the input to said modulation control voltage Vm(t), is adapted to generate at the output a phase-shift modulation φm(t), said phase-shift modulation φm(t) introducing between said two counter-propagating waves (24, 25) a phase-difference modulation Δφm(t) such that: Δφm(t)=φm(t)−φm(t−Δτg), Δτg=1/(2fp) being the transit-time difference between said two counter-propagating waves (24, 25) determined between said phase modulator (33) and said splitting element (23), and signal processing means (110) including:
an analog/digital converter (111) digitizing said modulated electrical signal (38) received from the detector (14) and representative of said power received to deliver a digital electrical signal, anda digital processing unit (112) adapted to process said digital electrical signal to deliver a signal function of said phase difference Δφp and of said parameter to be measured, feedback means (120) adapted to process said signal function of said phase difference A to generate a feedback signal, biasing means (130) adapted to generate a biasing signal, means (140) for controlling said modulation chain (30), adapted to process said feedback signal and said biasing signal to deliver said digital control signal at the input of said modulation chain (30), such that said modulation control voltage Vm(t) at the input of said phase modulator (33) is the sum of a feedback modulation voltage Vcr(t) and a biasing modulation voltage Vb(t), said phase modulator (33) being adapted, when it is subjected to said feedback modulation voltage Vcr(t), to generate a feedback phase-shift modulation φcr(t) (121), said feedback phase-shift modulation φcr(t) (121) introducing a feedback phase-difference modulation Δφcr between said two counter-propagating waves (24, 25) allowing to keep at zero the sum of said phase difference Δφp and said feedback phase-difference modulation Δφcr, and means (150) for controlling the gain of said modulation chain (30) allowing to keep adjusted the transfer function of said modulation chain (30),said fiber-optic measurement device (10) being characterized in that said biasing means (130) are adapted to generate said biasing signal such that said phase modulator (33) generates a biasing phase-shift modulation φb(t), when it is subjected to said biasing modulation voltage Vb(t), said biasing phase-shift modulation φb(t) being the sum of:
a first biasing phase-shift modulation component φb1(t) (34A), introducing a first biasing phase-difference modulation component Δφb1(t) (34) between said two counter-propagating waves (24, 25), said first biasing phase-difference modulation component Δφb1(t) (34) being a square-wave periodic modulation, of levels +π and −π, at a first biasing modulation frequency fb1 such that fb1=(2k1+1) fp, k1 being a natural number and fp said proper frequency, and a second biasing phase-shift modulation component φb2(t) (35A), introducing a second biasing phase-difference modulation component Δφb2(t) (35) between said two counter-propagating waves (24, 25), said second biasing phase-difference modulation component Δφb2(t) (35) being a periodic modulation, of extreme amplitudes +π/a and −π/a, a being a non-zero real number such that |a|>1, at a second biasing modulation frequency fb2 such that fb2=(2k2+1) fp, k2 being a non-zero natural number such that k2>k1, and fp said proper frequency. |
