Fully integrated microwave frequency synthesizer on heterogeneous silicon-III/V.

We demonstrate a photonic microwave generator on the heterogeneous silicon-InP platform. Waveguide photodiodes with a 3 dB bandwidth of 65 GHz and 0.4 A/W responsivity are integrated with lasers that tune over 42 nm with less than 150 kHz linewidth. Microwave signal generation from 1 to 112 GHz is achieved.

Integrated chip-scale Si3N4 wavemeter with narrow free spectral range and high stability.

We designed, fabricated, and characterized an integrated chip-scale wavemeter based on an unbalanced Mach-Zehnder interferometer with 300 MHz free spectral range. The wavemeter is realized in the Si3N4 platform, allowing for low loss with ∼62 cm of on-chip delay. We also integrated an optical hybrid to provide phase information. The main benefit of a fully integrated wavemeter, beside its small dimensions, is increased robustness to vibrations and temperature variations and much improved stability over fiber-based solutions.

Polarization demultiplexing in Stokes space.

A technique is demonstrated for polarization demultiplexing of arbitrary complex-modulated signals. The technique is based entirely on the observation of samples in Stokes space, does not involve demodulation and is modulation format independent. The data in Stokes space is used to find the best fit plane and the normal to it which contains the origin. This normal identifies the two orthogonal polarization states of transmission and the desired polarization alignment transformation matrix. The technique is verified experimentally and is compared with the constant modulus algorithm.

Kalman filter carrier and polarization-state tracking.

Application of Kalman filtering with a novel nearest-symbol constraint enables dynamic tracking of carrier phase and polarization state. Thereby, the proposed Kalman filter accomplishes demodulation of optical polarization-multiplexed complex modulation format signals.

Fast polarization-dependent loss measurement based on continuous polarization modulation.

A new technique for measuring the insertion loss and the polarization-dependent loss (PDL) of optical components is proposed. The technique is based on continuous polarization modulation of the stimulus optical field as opposed to sequential polarization state switching as in the traditional Jones matrix analysis or Mueller matrix methods. This new method relies on the simultaneous observation of multiple harmonics of the transmitted optical signal in the frequency domain. The physical theory of this method is presented along with PDL measurements performed on a polarization modulator, a polarizer, a PDL standard, and on an acetylene absorption cell exhibiting spectrally sharp insertion loss features.

Polarization mode dispersion measurement based on continuous polarization modulation.

A novel technique is proposed for measurement of the group delay (GD) and the differential group delay (DGD) of optical material, components, and fiber. This new method is based on continuous polarization modulation of the stimulus optical field as opposed to sequential polarization state switching used in the traditional phase shift method. A new complete derivation of the phase shift method, based on the modified Jones calculus of elementary matrices, is presented. The derivation reveals that the phase shift measurement actually depends on all eight elementary parameters that represent DGD and optical frequency derivatives of polarization-dependent loss (PDL). Thus, the new expression for the phase shift includes the combined effect of PDL and DGD. The proposed method is evaluated by measuring a section of polarization-maintaining fiber and a 50 km length of single-mode fiber over a wavelength range from 1530 to 1610 nm. Measurements of DGD in a long single-mode fiber are shown to be highly insensitive to environmentally induced GD drift.

Frequency resolution and amplitude accuracy of the coherent optical spectrum analyzer with a swept local oscillator.

We present a model for coherent optical spectrum analysis that relates the key parameters of frequency resolution, power uncertainty, and sweep speed. The theoretical model is compared with experimental results obtained from spectral measurements of an external-cavity laser.