Fiber-based optical modulator
Methods, apparatus, and systems for modulation of a laser beam. An optical modulator may comprise an optical input to receive an optical beam, and one or more lengths of fiber between the optical input and an optical output. At least one of the lengths of fiber comprises a confinement region that is optically coupled to the output. The optical modulator may further comprise a perturbation device to modulate, through action upon the one or more lengths of fiber, a transmittance of the beam through the confinement region from a first transmittance level at a first time instance to a second transmittance level at a second time instance. The optical modulator may further comprise a controller input coupled to the perturbation device, wherein the perturbation device is to act upon the one or more lengths of fiber in response to a control signal received through the controller input.
1. An optical modulator, comprising:
an optical input to receive an optical beam;
one or more lengths of fiber between the optical input and an optical output, wherein the one or more lengths of fiber further comprise a first length of fiber directly end-coupled to a second length of fiber, and wherein the first length of fiber has a first refractive index profile (RIP) and the second length of fiber has a second RIP, wherein second RIP comprises a first confinement region and a second confinement region, at least one of the confinement regions being coupled to the optical output;
a perturbation device to modulate, through action upon the one or more lengths of fiber, a transmittance of the beam through the first and second confinement regions from first complementary transmittance levels at a first time instance to second complementary transmittance levels at a second time instance; and
a controller input coupled to the perturbation device, wherein the perturbation device is to act upon at least one of the one or more lengths of fiber in response to a control signal received through the controller input.
2. The optical modulator of claim 1 , wherein an optical power transmitted by a first of the first and second confinement regions to the optical output at the first time is at least 10% greater than the optical power transmitted through the first of the first and second confinement regions to the optical output at the second time, and wherein optical power transmitted by a second of the first and second confinement regions at the first time is less than the optical power transmitted through the second of the first and second confinement regions at the second time.
3. The optical modulator of claim 1 , wherein the action upon the one or more lengths of fiber alters:
a coupling of the optical beam between the first length of the fiber and the one of the first and second confinement regions of the second length of the fiber.
4. The optical modulator of claim 3 , wherein:
the action upon the one or more lengths of fiber alters a coupling of the optical beam from the first fiber length into the first confinement region;
the first levels of transmittance are associated with a greater coupling of the optical beam into the first confinement region; and
the second levels of transmittance are associated with a lesser coupling of the optical beam into the first confinement region.
5. The optical modulator of claim 1 , wherein one of the first and second confinement regions is more efficiently optically coupled to the output than the other of the first and second confinement regions.
6. The optical modulator of claim 1 , wherein:
the second confinement region is optically decoupled from the output;
the action upon the one or more lengths of fiber inversely alters coupling of the optical beam through the first and second confinement regions;
the first levels of transmittance are associated with a greater coupling of the optical beam into the first confinement region and a lesser coupling of the optical beam into the second confinement region; and
the second levels of transmittance are associated with a lesser coupling of the optical beam into the first confinement region and a greater coupling of the optical beam into the second confinement region.
7. The optical modulator of claim 6 , wherein the first confinement region is separated from the second confinement region by a cladding structure comprising a material having a lower refractive index than that of the first confinement region, and having a lower refractive index than that of the second confinement region.
8. The optical modulator of claim 7 , wherein the second confinement region comprises an annular structure co-axial with the first confinement region.
9. The optical modulator of claim 1 , wherein the first confinement region comprises a central core and the second confinement region is annular and encompasses the first confinement region.
10. The optical modulator of claim 9 , wherein:
the first length of fiber has a graded RIP in at least a radially central portion; and
the perturbation device is to modulate the transmittance through action upon at least the first length of fiber.
11. The optical modulator of claim 1 , wherein the perturbation device is to have at least a first state corresponding to the first complementary levels of transmittance and a second state corresponding to the second complementary levels of transmittance.
12. The optical modulator of claim 11 , wherein the perturbation device is to transition between the first and second states according to an analog waveform with the transmittance to vary according to a continuous function that includes the first and second levels of transmittance.
13. An optical system, comprising:
a laser; and
the optical modulator of claim 1 , wherein the optical input is coupled to an output coupler of the laser.