Fiber noise cancellation

A system for delivering stable laser light to a remote location via an optical fiber, the system comprising:

• an optical beam splitter/combiner configured to split a laser beam generated by a laser into a reference beam and a delivery beam, the delivery beam being coupled into an optical fiber for delivering the delivery beam to the remote location, a fraction of the delivery beam being reflected back from the remote location toward the optical beam splitter/combiner through the optical fiber;
• an acousto-optic modulator (AOM) configured to shift a frequency of the reference beam by a predetermined frequency interval, wherein the optical beam splitter/combiner is further configured to combine the reference beam that has been frequency-shifted and the reflected delivery beam to generate an interference beam;
• a photodetector configured to detect the interference beam to determine a phase difference between the reference beam and the reflected delivery beam due to noise added to the delivery beam while being transmitted through the optical fiber;
• and
• an offset cavity-lock coupled to the laser and a reference cavity, the offset cavity-lock configured to adjust a phase of the laser beam generated by the laser based on the phase difference to reverse a phase shift of the delivery beam induced by the noise added to the delivery beam while being transmitted through the optical fiber.

A method of delivering stable laser light to a remote location via an optical fiber, the method comprising:

• splitting a laser beam generated by a first laser into a reference beam and a delivery beam;
• coupling the delivery beam into the optical fiber for delivering the delivery beam to the remote location, a fraction of the delivery beam being reflected back from the remote location through the optical fiber;
• shifting a frequency of the reference beam by a predetermined frequency interval;
• generating an interference beam by combining the reference beam that has been frequency-shifted and the reflected delivery beam;
• detecting the interference beam to determine a phase difference between the reference beam and the reflected delivery beam due to noise added to the delivery beam while the delivery beam is transmitted through the optical fiber;
• and
• adjusting, via a phase-locked loop coupled to the first laser and a second laser, a phase of the laser beam based on the phase difference by locking the phase of the laser beam generated by the first laser to a phase of a stable laser beam generated by the second laser, thereby delivering a corrected laser beam to the remote location free of the noise while being transmitted through the optical fiber.

A system for delivering stable laser light to a remote location via an optical fiber, the system comprising:

• an optical beam splitter/combiner configured to split a laser beam generated by a first laser into a reference beam and a delivery beam, the delivery beam being coupled into the optical fiber for delivering the delivery beam to the remote location, a fraction of the delivery beam being reflected back from the remote location toward the optical beam splitter/combiner through the optical fiber;
• an acousto-optic modulator (AOM) configured to shift a frequency of the reference beam by a predetermined frequency interval, wherein the optical beam splitter/combiner is further configured to combine the reference beam that has been frequency-shifted and the reflected delivery beam to generate an interference beam;
• a photodetector configured to detect the interference beam to determine a phase difference between the reference beam and the reflected delivery beam due to noise added to the delivery beam while being transmitted through the optical fiber;
• and
• a phase-locked loop coupled to the first laser and a second laser, the phase-locked loop being configured to adjust a phase of the laser beam generated by the first laser based on the phase difference by locking the phase of the laser beam to a phase of a stable laser beam generated by the second laser, thereby delivering the delivery beam to the remote location free of the noise while being transmitted through the optical fiber.