Implementation and evaluation of a dual parallel linearization system for AM-SCM video transmission

Optical Comb Sources and High-Resolution Optical Filtering for Measurement of Photodiode Harmonic Distortion

“…Substituting (7) and (8) into (4) and (5) we see the measurement dynamic range and maximum measurable th-order intercept points are given by (9) and (10) where is the thermal noise current delivered to the load; this current becomes negligible for photocurrents above 1.0 mA. The key point here is that the measurable intercept point and average photocurrent are linked-to accurately measure the intercept requires that the average photocurrent is sufficiently high to bring the nonlinear sidebands above the noise floor.…”

“…As a result, there has been much interest in achieving very low halfwave voltages (a measure of modulator efficiency) and very high average photocurrent levels as these enable extremely low noise figure analog links [7], [8]. In addition to increased modulator efficiency, there is also significant interest in improving link linearity by mitigating the inherent nonlinearity of the MZM through the use of various linearized modulators [9], [10], the wavelength- [11] or polarization-dependence [12] of Mach-Zehnder modulators, or through linearized phase-modulated links [13]- [15]. While these techniques have been utilized to achieve spur(ious)-free dynamic ranges in excess of 130 dB (in a 1-Hz bandwidth), such demonstrations have only been performed in modest-photocurrent links ( mA).…”

The Reduction of Harmonic and Intermodulation Distortions with a Cascaded Mach-Zehnder Molulator

“…In this study, the second and third nonlinear distortions are considered as dominant terms and higher order nonlinear terms are neglected. We get: the fundamental terms P~ , = -0.5bl cos2 e L J1 (XI )+a2 Jo (X2) Jl (XI )] '(2) Pw' = ~ b3sin2 6Jl (X3 ) O 5b cos e[J (X )+alJo(Xl)Jl(X )] .…”

Dynamic Range Improvement of IM-DD Optical Link using Dual-Wavelength Dual-Parallel Modulation

“…Generally, the third-order intermodulation distortion (IMD3) is the main restricting factor of the SFDR, which is inherently introduced by the nonlinear transfer function of an MZM. Therefore, numerous methods have been proposed to suppress the IMD3 of the IMDD links, including predistortion linearization [2][3][4][5], polarization mixing [6][7], dual-wavelength input [8][9], dual-serial modulation [10][11] and dual-parallel modulation (DPM) [12][13][14]. The predistortion linearization reduces the distortion in the electronic domain, and its electric circuit is usually complicated.…”

“…In the coherent DPM, the optical power is asymmetrically divided by a polarization-maintaining optical coupler, then fed into two MZMs respectively, and finally recombined by an optical coupler. An optical phase shifter is required to maintain the quadrature between the outputs of the two MZMs in order to prevent the recreation of distortion products [13]. Considering the high sensitivity of the optical phase on the disturbance of the environment, a feedback loop controller is needed to actively adjust the phase shifter.…”