Optical transceiver and method of operation thereof

• US 8,866,058 B2
• Filed: 07/22/2010
• Issued: 10/21/2014
• Est. Priority Date: 08/04/2009
• Status: Expired due to Fees

• Current Assignee: Northrop Grumman Litef Gmbh (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Litef Gmbh (Northrop Grumman Corporation)
• Inventors: Voigt, Sven
• Primary Examiner(s): LUU, THANH X
• Application Number:
  US13/261,171
• Publication Number:
  US 20120199722A1
• Time in Patent Office: 1,552 Days
• Field of Search: 250/205, 356/460
• US Class Current: 250/205
• CPC Class Codes: G01C 19/721 Details
• CPC Class Codes: H04B 10/572 Wavelength control

Abstract

An optical transceiver comprises a substrate having a temperature control device, a light source, a light-guiding fiber, a detector, optics for collimating the light from the light source, coupling optics for focusing the light beam into the light-guiding fiber, and a beamsplitter which sends one part of the collimated light beam into a wavelength stabilization unit and another part of the collimated light beam into the coupling optics. A wavelength stabilization unit detects and compensates for wavelength drift of the light source. The optical transceiver has a superluminescent diode for its light source and may, for example, be integrated in a fiber-optic gyro.

Claims

1. An optical transceiver comprising:

a light source which can be controlled by a driver current and emits light, which is radiated by the optical transceiver;

a wavelength stabilization unit for stabilizing the wavelength of the light emitted by the light source, comprising;

a sensor device for detecting a wavelength drift;

a control unit connected to the sensor device and the light source for controlling the driver current as a function of the sensor signals so as to counteract a drift of the wavelength, wherein

the wavelength stabilization unit comprises a wavelength sensor for determining a central wavelength of the emitted light and a regulating circuit for compensating for a wavelength drift of the emitted light,

the wavelength sensor comprises two photodiodes of different spectral sensitivity;

characterized in that

the optical transceiver comprises a detector for measuring light received by the optical transceiver, an amplifier for amplifying an electrical output signal of the detector with a switchable gain, and a control circuit which is suitable for controlling the gain as a function of a sum signal of output signals of the two photodiodes.

2. The optical transceiver as claimed in claim 1, characterized in that

the light source is a broadband semiconductor light source.

3. The optical transceiver as claimed in claim 1, characterized in that

the light source is a superluminescent diode.

4. The optical transceiver as claimed in claim 3, characterized in that

an emission spectrum of the light source lies below a wavelength of 1000 nm.

5. The optical transceiver as claimed in claim 1, characterized in that

the regulating circuit is configured to form a ratio signal of output signals of the two photodiodes and to control the driver current so that a value of the ratio signal determined during calibration remains constant.

6. The optical transceiver as claimed in claim 1, characterized by

a polarization device which is provided between the light source and the detector.

7. The optical transceiver as claimed in claim 6, characterized in that

the polarization device comprises two polarizers at two positions, the first position being provided in the collimated light beam path between the light source and a beamsplitter and the second position being provided between the beamsplitter and the detector.

8. The optical transceiver as claimed in claim 1, characterized in that

a polarizer is provided between the beamsplitter and the light-guiding fiber.

9. The optical transceiver as claimed in claim 1, characterized by a temperature control device having

a temperature sensor which detects temperature variations;

and

a thermoelectric cooler which balances temperature variations.

10. An operating method for an optical transceiver, comprising the steps of:

determining a current central wavelength of an emission band of a light source of the optical transceiver;

comparing the current central wavelength with a reference central wavelength of the emission band;

controlling the light source so that the current central wavelength of the emission band is brought to coincide with the reference central wavelength, wherein the current central wavelength is determined from a ratio signal formed from output signals of two photodiodes of different spectral sensitivity, to which the light from the light source is incident; and

controlling a gain of a detector of the optical transceiver as a function of a sum signal formed from the output signals of the two photodiodes of different spectral sensitivity.

11. The operating method as claimed in claim 10, characterized in that

the reference central wavelength of the emission band is determined in a calibration step.

12. The operating method as claimed in claim 10, characterized in that

the light source is controlled by means of a driver current which is delivered to the light source and imposes a current across a pn junction in the light source.

13. The operating method as claimed in claim 12, characterized in that

a working point of the light source is selected so that a shift of the emission band to longer wavelengths can be compensated for by increasing the driver current.

14. The operating method as claimed in claim 12, characterized in that

a working point of the light source is selected so that a shift of the emission band to longer wavelengths can be compensated for by reducing the driver current.

15. A fiber optic gyroscope comprising:

an optical transceiver including;

a light source which can be controlled by a driver current and emits light, which is radiated by the optical transceiver; and

a wavelength stabilization unit for stabilizing the wavelength of the light emitted by the light source,

said wavelength stabilization unit including;

a sensor device for detecting a wavelength drift;

a control unit connected to the sensor device and the light source for controlling the driver current as a function of the sensor signals so as to counteract a drift of the wavelength wherein said wavelength stabilization unit comprises a wavelength sensor for determining a central wavelength of the emitted light and a regulating circuit for compensating for a wavelength drift of the emitted light,

said wavelength sensor comprising two photodiodes of differing spectral sensitivities,

a detector for measuring light received by the optical transceiver,

an amplifier for amplifying an electrical output signal of the detector with a switchable gain, and

a control circuit which is suitable for controlling the gain as a function of a sum signal of output signals of the two photodiodes,

a divider arranged to receive a beam of wavelength-stabilized light output from said transceiver, split said beam into a pair of sub-beams, then recombine said sub-beams upon exiting a loop of optical fiber and to direct said recombined beam to said detector of said optical transceiver,

said loop of optical fiber being arranged to receive said pair of sub-beams at opposed ends to counterpropagate therein,

so that a phase shift between the sub-beams is detected as an interference pattern indicative of rotation rate by said detector.

16. The fiber optic gyroscope as defined in claim 15 additionally comprising

said divider comprises an integrated optical chip having a polarization axis,

an optical fiber having the polarization axis of said integrated optical chip guides light between said transceiver and said integrated optical chip.

17. A navigation system comprising

at least one fiber optic gyroscope, said at least one fiber optic gyroscope comprising:

an optical transceiver including;

a light source which can be controlled by a driver current and emits light, which is radiated by the optical transceiver; and

a wavelength stabilization unit for stabilizing the wavelength of the light emitted by the light source,

said wavelength stabilization unit including;

a sensor device for detecting a wavelength drift;

a control unit connected to the sensor device and the light source for controlling the driver current as a function of the sensor signals so as to counteract a drift of the wavelength wherein said wavelength stabilization unit comprises a wavelength sensor for determining a central wavelength of the emitted light and a regulating circuit for compensating for a wavelength drift of the emitted light,

said wavelength sensor comprising two photodiodes of differing spectral sensitivities,

a detector for measuring light received by the optical transceiver,

an amplifier for amplifying an electrical output signal of the detector with a switchable gain, and

a control circuit which is suitable for controlling the gain as a function of a sum signal of output signals of the two photodiodes,

a divider arranged to receive a beam of wavelength-stabilized light output from said transceiver, split said beam into a pair of sub-beams, then recombine said sub-beams upon exiting a loop of optical fiber and to direct said recombined beam to said detector of said optical transceiver,

said loop of optical fiber being arranged to receive said pair of sub-beams at opposed ends to counterpropagate therein,

so that a phase shift between the sub-beams is detected as an interference pattern indicative of rotation rate with respect to at least one axis by said detector.