US 12,174,066 B2
Reducing polarization dependent loss (PDL) in a grating-based optical spectrum analyzer (OSA)
Driss Touahri, Nepean (CA); Christopher Russell Wagner, Kanata (CA); and Joshua Benjamin Julius Philipson, Ottawa (CA)
Assigned to VIAVI SOLUTIONS INC., Chandler, AZ (US)
Filed by VIAVI SOLUTIONS INC., Chandler, AZ (US)
Filed on Oct. 13, 2023, as Appl. No. 18/486,355.
Application 18/486,355 is a continuation of application No. 17/334,132, filed on May 28, 2021, granted, now 11,828,648.
Prior Publication US 2024/0110831 A1, Apr. 4, 2024
Int. Cl. G01J 3/02 (2006.01); G01J 3/14 (2006.01); G01J 3/18 (2006.01); G01J 3/447 (2006.01)
CPC G01J 3/0224 (2013.01) [G01J 3/14 (2013.01); G01J 3/18 (2013.01); G01J 3/447 (2013.01)] 20 Claims
OG exemplary drawing
 
20. A multi-pass optical spectrum analyzer (OSA), comprising:
an optical configuration comprising:
a polarization scrambling element to receive and scramble an input optical beam, and to output a polarization scrambled input beam;
a birefringent element to receive the polarization scrambled input beam and split the polarization scrambled input beam into two exit beams, the birefringent element comprising:
a first birefringent wedge having a first optical axis and comprising a hypotenuse surface; and
a second birefringent wedge having a second optical axis and comprising a hypotenuse surface,
wherein the hypotenuse surface of the first birefringent wedge is attached to the hypotenuse surface of the second birefringent wedge such that the first optical axis is not parallel to the second optical axis, and
wherein the input optical beam traverses the first birefringent wedge, the cemented hypotenuse surfaces of the first birefringent wedge and the second birefringent wedge, and the second birefringent wedge, to become the two exit beams, the two exit beams comprising:
a first exit beam having a first polarization state and a first direction; and
a second exit beam having a second polarization state different from the first polarization state and a second direction diverging from the first direction; and
optics to receive and to transform at least one of the first exit beam and the second exit beam such that the two exit beams are parallel and have the same polarization state;
a grating element to receive and diffract the two parallel exit beams having the same polarizations, and to output diffracted beams therefrom; and
a retroreflective element to receive the output diffracted beams and reflect back the diffracted beams to the grating element such that the input optical beam passes through the grating element two or more times.