Elimination of optical ghosts in optical spectral analyzers through a scanning spectral filter
AssigneeViavi Solutions Inc.
InventorsDriss Touahri, Luis Andre Neves Paiva Fernandes
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Abstract
A monochromator apparatus in a grating-based optical spectrum analyzer (OSA) includes a diffraction grating, a reflector element, and a tunable spectral filter. The tunable spectral filter may include a band-pass filter, a low-pass filter, a high-pass filter, or a linear variable filter, for example. A spectral window of the filter may move synchronously with the scanning spectral window of the OSA. A high-pass filter implementation may be introduced during a subsequent portion of the OSA window before the optical ghost signal starts appearing. The filter may either be linearly scanned across the optical beam, angularly tuned, or introduced in a subsequent portion of the OSA scanning window.
Claims20
A system, comprising:
- a grating element to receive an input optical beam via an input element and diffract the input optical beam;
- a reflector element to receive the diffracted input optical beam from the grating element and reflect the diffracted input optical beam back onto the grating element, wherein the grating element is to diffract the reflected input optical beam and transmit the diffracted reflected input optical beam as an output optical beam to an output element;
- a tunable spectral filter element positioned on a path of the output optical beam to reduce or eliminate a ghost signal beam;
- and
- a motion element connected to move the tunable spectral filter element to adjust a cut-off point or a band of the tunable spectral filter element based on a wavelength of the input optical beam to allow the output optical beam to pass through the tunable spectral filter element to the output element and prevent the ghost signal beam from passing through the tunable spectral filter element to the output element.
A method for an optical spectrum analyzer, comprising:
- receiving, at a grating element, a main optical beam from an input element to be diffracted by the grating element;
- diffracting, by the grating element, the main optical beam onto a reflector element;
- reflecting, by the reflector element, the diffracted main optical beam as a reflected main optical beam back to the grating element;
- diffracting, by the grating element, the reflected main optical beam from the reflector element, wherein the grating element is to transmit the diffracted reflected main optical beam as an output optical beam toward an output element;
- positioning a tunable spectral filter element on a path of the output optical beam to reduce or eliminate a ghost signal beam;
- moving, by a motion element, the tunable spectral filter element to adjust a cut-off point or a band of the tunable spectral filter element based on a wavelength of the main optical beam to allow the output optical beam to pass through the tunable spectral filter element to the output element and prevent the ghost signal beam from passing to the output element;
- and
- transmitting, by the grating element, the diffracted reflected main optical beam as the output optical beam to the output element via the tunable spectral filter element.
An optical spectrum analyzer (OSA), comprising:
- an optical pre-processing block comprising:
- an input element;
- an output element;
- a grating element to receive an input optical beam via the input element and diffract the optical beam;
- a reflector element to receive the diffracted input optical beam from the grating element and reflect the diffracted input optical beam back onto the grating element,
- wherein the grating element is to diffract the reflected input optical beam and transmit the diffracted reflected input optical beam as an output optical beam toward the output element;
- a tunable spectral filter element positioned on a path of the output optical beam to reduce or eliminate a ghost signal beam;
- and
- a motion element connected to move the tunable spectral filter element to adjust a cut-off point or a band of the tunable spectral filter element based on a wavelength of the input optical beam to allow the output optical beam to pass through the tunable spectral filter element to the output element and prevent the ghost signal beam from passing to the output element.
Dependencies are inferred from the claim text.