Tunable long-period optical grating device and optical systems employing same

A device for tuning the wavelength response of an optical fiber having a long-period grating region with spaced-apart perturbations, the device comprising a substrate for securing the optical fiber and a mandrel for winding the optical fiber, wherein the fiber is fixedly secured adjacent one end of the grating region to the substrate and is secured adjacent the other end of the grating region to the mandrel so that when the mandrel rotates, it winds or unwinds the fiber, thereby changing the spacing between the perturbations of the long-period grating region.

An improved optical communications system of the type having a transmitter source for emitting an optical signal, a signal path comprising an optical fiber, a receiver, an amplifier disposed in the optical signal path for amplifying the transmitted signal, a pump source for pumping the amplifier, and a long-period fiber grating disposed in the optical fiber for equalizing the gain of the amplifier, the improvement comprising the device according to claim 8 for tuning the at least one optical fiber grating.

A device for tuning an optical fiber having a long-period grating region with spaced-apart perturbations, the device comprising:

• a pair of magnets secured to the fiber adjacent the grating region and aligned so that their magnetic poles are disposed on a horizontal plane substantially parallel with the axis of the fiber, the magnets having a gap of less than 0.50 inches between them, and
• an electromagnet for applying a magnetic field to the magnets to cause them to move relative to each other, thereby changing the spacing between the perturbations of the long-period grating region,
• in which an AC demagnetizing field and a DC pulse current are alternatively applied to the electromagnet to provide a bistably tuned device.

A device for tuning an optical fiber having a long-period grating region with spaced-apart perturbations, the device comprising:

• a pair of magnets secured to the fiber adjacent the grating region and aligned so that their magnetic poles are disposed on a horizontal plane substantially parallel with the axis of the fiber, the magnets having a gap of less than 0.50 inches between them, and
• an electromagnet for applying a magnetic field to the magnets to cause them to move relative to each other, thereby chancing the spacing between the perturbations of the long-period grating region,
• in which the magnetic field is removed so that the strain-inducing body exhibits a remanent strain upon the fiber.

A device for tuning an optical fiber having a lon-period grating region with spaced-apart perturbations, the device comprising:

• a temperature-sensitive body having a predetermined coefficient of thermal expansion, the temperature-sensitive body being secured to the optical fiber adjacent the long-period grating region for transmitting strain to the fiber;
• and
• a heating element disposed adjacent the temperature-sensitive body for adjusting the temperature of the temperature-sensitive body and cause the temperature-sensitive body to place strain on the fiber, thereby changing the spacing between the perturbations of the long-period grating region.

An improved optical communications system of the type having a transmitter source for emitting an optical signal, a signal path comprising an optical fiber, a receiver, an amplifier disposed in the optical signal path for amplifying the transmitted signal, a pump source for pumping the amplifier, and a long-period fiber grating with spaced-apart perturbations disposed in the optical fiber for equalizing the gain of the amplifier, the improvement comprising a device for tuning the at least one optical fiber grating, the device comprising:

• a strain-inducing body secured to the optical fiber adjacent the long-period grating region for transmitting strain to the fiber;
• and
• a force-generating body disposed adjacent the strain-inducing body for interacting with the strain-inducing body to generate a force for causing the strain-inducing body to place strain on the fiber, thereby changing the spacing between the perturbations of the long-period grating region.