The integrated electro-optic modulator plays an important role in the broadband wireless communication and phase-coded radar etc. The electro-optic modulator using a lithium niobite (LN) ridge waveguide is easy to be integrated and has excellent electro-optic response. However, its fabrication and coupling still face great challenge. In this paper, an intensity modulator (IM) based on heterogeneous platform with LN and silicon nitride (Si3N4) is designed. The optical mode field distribution is simulated as the waveguide size changes. The parameters such as the width and height of loadinged strip are optimized to ensure that the light power is highly concentrated in the LN layer (over 90%). The propagation loss of the IM with different Y-junction shapes is analyzed. In addition, the influence of different electrode parameters on half-wave voltage is discussed systematically. The results demonstrate that the designed IM has a low half wave voltage of 2.1V, characteristic impedance of 53Ω and propagation loss of -0.2dB. The proposed IM has the advantages of convenient fabrication and coupling, which provides an alternative modulation unit for multi-level or large-scale modulation integrated chips.
A triple-frequency microwave photonic link is proposed based on a polarization-multiplexing dual-parallel Mach- Zehnder modulator (PM-DPMZM). The lower sub-DPMZM is biased at the maximum transmission point to obtain the 2nd-order RF sidebands. Meanwhile, the RF signal modulates the upper sub-DPMZM through an electrical 90° hybrid coupler. The upper sub-DPMZM works at the carrier-suppressed single-sideband (CS-SSB) modulation to obtain the +1st order RF sideband. An optical band pass filter is used to filter out the +2nd-order RF sideband, and only the +1storder and -2nd-order RF sidebands are output for the frequency beating at a photodetector (PD). The frequency triple signal of 3ωRF is obtained correspondingly. The experimental link is built. The results show that the RF signal from 8 to 12 GHz is tripled, and frequency tripled signal at 24 to 36 GHz is acquired. The minimal spur suppression ratio of triple-frequency signal is 20dB. A relatively low-frequency signal can be used to generate a high-frequency signal with well quality by this triple-frequency link. The proposed method can be applied in various microwave photonic transmitting systems.
A reconfigurable microwave photonic frequency upconverter with local oscillator (LO) doubling or LO quadrupling is proposed based on two cascaded dual-parallel Mach–Zehnder modulators (DPMZMs) and a fiber Bragg grating (FBG) with a wide bandwidth (0.4 nm). The first DPMZM is used to generate the ±1st-order or ±2nd-order sidebands of the LO signal. The FBG is inserted to separate the positive and negative sidebands. Only the transmitted LO sideband is sent to the second DPMZM, and the carrier-suppressed single-sideband (CS-SSB) modulation of the intermediate frequency (IF) signal is realized by using an electrical 90 deg hybrid coupler. The reflected LO sideband via FBG and the −1st-order IF sideband are combined. Then, the upconverted signal with the frequency of 2ωLO + ωIF or 4ωLO + ωIF can be generated by a photodetector. The experimental results show that the spur suppression ratios of the upconverter with LO doubling and quadrupling are 21.3 and 11.3 dB, respectively. The proposed approach greatly reduces the frequency requirement of the LO signal. The purity of electrical spectrum is largely improved in both the LO doubling and LO quadrupling upconversion benefiting from the CS-SSB modulation. Furthermore, these two upconversion modes can be easily switched by tuning the DC biases of the first DPMZM.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.