Even-order harmonic cancellation for off-quadrature biased Mach-Zehnder modulator with improved RF metrics using dual wavelength inputs and dual outputs

Abstract

We present a technique using a dual-output Mach-Zehnder modulator (MZM) with two wavelength inputs, one operating at low-bias and the other operating at high-bias, in order to cancel unwanted even-order harmonics in analog optical links. By using a dual-output MZM, this technique allows for two suppressed optical carriers to be transmitted to the receiver. Combined with optical amplification and balanced differential detection, the RF power of the fundamental is increased by 2 dB while the even-order harmonic is reduced by 47 dB, simultaneously. The RF noise figure and third-order spurious-free dynamic range (SFDR(3)) are improved by 5.4 dB and 3.6 dB, respectively. Using a wavelength sensitive, low V(pi) MZM allows the two wavelengths to be within 5.5 nm of each other for a frequency band from 10 MHz to 100 MHz and 10 nm for 1 GHz.

Photonics-Assisted Super-Octave Microwave Phase Shifter

“…To suppress SDs, the most commonly used method is differential detection [19], [20], [22]. In this method, a balanced photodetector (BPD) is used to recover the RF signal.…”

Multi-octave linearized analog photonic link based on a polarization-multiplexing dual-parallel Mach-Zehnder modulator

“…On the other hand, some efforts have been devoted to suppress the IMD2 of the analog photonic link [16][17][18]. The key idea is to implement two intensity modulations, which would produce two complementary IMD2 if the modulated signals are sent to the photodetectors (PDs).…”

Simultaneous even- and third-order distortion suppression in a microwave photonic link based on orthogonal polarization modulation, balanced detection, and optical sideband filtering

“…For the approaches in [6] and [7], two matched MZMs are needed, which makes the system complicated. A simpler approach is to utilize a single dual-output MZM with dual optical inputs and dual optical outputs [8]. Since the transfer function of a MZM is wavelength dependent, by choosing the two wavelengths with a proper wavelength spacing, the bias points for the two wavelengths can be controlled at the opposite quadrature points.…”

“…Of course, the bandwidth of the electrical hybrid will limit the bandwidth of the MPL. All the MPLs reported in [6][7][8][9] are able to operate with significantly reduced evenorder distortions, but the odd-order distortions are still there which will affect the microwave signal power accommodating capacity of the MPLs.…”