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OPTICS LETTERS / Vol. 39, No. 1 / January 1, 2014
Optical-to-RF phase shift conversion-based microwave photonic phase shifter using a fiber Bragg grating Xudong Wang, Erwin H. W. Chan,* and Robert A. Minasian School of Electrical and Information Engineering, Institute of Photonics and Optical Sciences, University of Sydney, Sydney, NSW 2006, Australia *Corresponding author: [email protected] Received September 3, 2013; revised October 24, 2013; accepted November 6, 2013; posted November 22, 2013 (Doc. ID 196745); published December 24, 2013 A novel microwave photonic phase shifter structure is presented. It is based on the conversion of the optical carrier phase shift into an RF signal phase shift via controlling the carrier wavelength of a single-sideband RF-modulated optical signal into a fiber Bragg grating. The new microwave photonic phase shifter has a simple structure and only requires a single control to shift the RF signal phase. It also has the ability to realize multiple phase shifts. Experimental results demonstrate a continuous 0°–360° phase shift with low amplitude variation of 98% reflectivity and a length of 10 mm. Note that the phase response of the grating was not point symmetrical about the center frequency, as shown in Fig. 4. This is believed to be due to the residual chirp, which was often included during the grating fabrication process, as explained in [13]. The optical signal reflected by the fiber Bragg grating was detected by a photodetector, and the microwave photonic phase shifter amplitude and phase responses were measured using a network analyzer. Tuning the laser wavelength (or frequency) between the two dotted lines in Fig. 4, which corresponds to around 0.11 nm wavelength tuning, caused 0°–180° phase changes in the optical carrier. This resulted in a continuous 0°–180° output RF signal phase shift. The measured microwave photonic phase shifter output amplitude and phase responses are shown in Fig. 6. The DPMZM bias voltages were then switched to V 1 −2.63 V, V 2 1.83 V, and V 3 1.86 V. This caused the 0° phase shift in the original bias voltage setting to become a −180° phase shift. A measured continuous −180° to 0° phase shift, having the amplitude and phase responses shown in Fig. 6, was obtained by tuning the laser wavelength (or frequency) between the two dotted lines in Fig. 4. This verifies the concept of the optical-to-RF phase shift conversion technique using a single fiber Bragg grating. The measurements show only 1.7 dB amplitude variation and
OPTICS LETTERS / Vol. 39, No. 1 / January 1, 2014
Optical-to-RF phase shift conversion-based microwave photonic phase shifter using a fiber Bragg grating Xudong Wang, Erwin H. W. Chan,* and Robert A. Minasian School of Electrical and Information Engineering, Institute of Photonics and Optical Sciences, University of Sydney, Sydney, NSW 2006, Australia *Corresponding author: [email protected] Received September 3, 2013; revised October 24, 2013; accepted November 6, 2013; posted November 22, 2013 (Doc. ID 196745); published December 24, 2013 A novel microwave photonic phase shifter structure is presented. It is based on the conversion of the optical carrier phase shift into an RF signal phase shift via controlling the carrier wavelength of a single-sideband RF-modulated optical signal into a fiber Bragg grating. The new microwave photonic phase shifter has a simple structure and only requires a single control to shift the RF signal phase. It also has the ability to realize multiple phase shifts. Experimental results demonstrate a continuous 0°–360° phase shift with low amplitude variation of 98% reflectivity and a length of 10 mm. Note that the phase response of the grating was not point symmetrical about the center frequency, as shown in Fig. 4. This is believed to be due to the residual chirp, which was often included during the grating fabrication process, as explained in [13]. The optical signal reflected by the fiber Bragg grating was detected by a photodetector, and the microwave photonic phase shifter amplitude and phase responses were measured using a network analyzer. Tuning the laser wavelength (or frequency) between the two dotted lines in Fig. 4, which corresponds to around 0.11 nm wavelength tuning, caused 0°–180° phase changes in the optical carrier. This resulted in a continuous 0°–180° output RF signal phase shift. The measured microwave photonic phase shifter output amplitude and phase responses are shown in Fig. 6. The DPMZM bias voltages were then switched to V 1 −2.63 V, V 2 1.83 V, and V 3 1.86 V. This caused the 0° phase shift in the original bias voltage setting to become a −180° phase shift. A measured continuous −180° to 0° phase shift, having the amplitude and phase responses shown in Fig. 6, was obtained by tuning the laser wavelength (or frequency) between the two dotted lines in Fig. 4. This verifies the concept of the optical-to-RF phase shift conversion technique using a single fiber Bragg grating. The measurements show only 1.7 dB amplitude variation and
