G. Ning

Spectral-resolved backreflection measurement of polarization mode dispersion in optical fibers

An improved backreflection technique is proposed to perform the spectral-resolved measurement of polarization mode dispersion (PMD) in optical fibers. This technique is based on the PMD dynamical equation and realized by measuring the polarization state evolutions of the reflected signal in both frequency and time domains. Two experimental setups, employing the far-end Fresnel reflection, are constructed to verify this technique. The agreement between the results of the proposed backreflection technique and the conventional forward technique is observed.

Generalized Mueller matrix method for polarization mode dispersion measurement in a system with polarization-dependent loss or gain

A generalized Mueller matrix method (GMMM) is proposed to measure the polarization mode dispersion (PMD) in an optical fiber system with polarization-dependent loss or gain (PDL/G). This algorithm is based on the polar decomposition of a 4X4 matrix which corresponds to a Lorentz transformation. Compared to the generalized Poincaré sphere method, the GMMM can measure PMD accurately with a relatively larger frequency step, and the obtained PMD data has very low noise level.

Tunable photonic microwave bandpass filter using phase Modulation and a chirped fiber grating in a Sagnac loop

We propose a novel all-optical microwave bandpass filter configuration, which uses phase modulation and a linearly chirped fiber grating in a Sagnac loop. The free spectral range (FSR) of the filter can be tuned continuously by tuning the grating. We also derive an expression for the filter transfer function. Calculated and measured results, which agree well, are presented to show a large notch rejection and an easily tunable FSR.

Switchable Coherence-Free Microwave Photonic Notch Filter Using a Pair of Intensity Modulators

A simple switchable coherence-free microwave photonic filter configuration is presented. It is based on a pair of intensity modulators modulating an optical signal at different times. The design is free from the velocity mismatch problem of an electrooptic modulator. This all-optical structure realizes two-tap filters with the capability of switching the sign of one of the taps to positive or negative. The sign depends on whether the linear slopes of the transfer functions of the two intensity modulators at their respective bias points are the same or opposite. The case of a phase shift between the two radio-frequency drive signals is also considered. Measured results confirm the theoretical expressions and demonstrate a stable switchable notch filter response.

Generation of Different Modulation Formats Using Sagnac Fiber Loop With One Electroabsorption Modulator

A simple structure is proposed to generate different modulation formats using a single electroabsorption modulator (EAM). The configuration is based on a Sagnac loop containing two polarization controllers and an EAM which modulates the clockwise and counterclockwise propagating waves inside the Sagnac loop. Measured results demonstrate switchable single-sideband suppression for both reflected and transmitted signals. The second-order harmonic suppression and carrier suppressed modulation are also achieved. A simple analysis explains most of the observed effects.

Multiple Dual-Wavelengths Erbium-Doped Fiber Ring Laser Using a Polarization-Maintaining Fabry–PÉrot Filter

A multiple dual-wavelengths erbium-doped fiber laser is demonstrated. It is designed by using a narrowband polarization-maintaining Fabry–PÉrot filter in a ring cavity. More than 30 power equalized dual-wavelengths are achieved in a 10-nm range. The switchability from multiple dual-wavelengths to normal multiple wavelengths laser is also demonstrated experimentally.

A microwave photonic filter using a switchable multiple dual-wavelength erbium-doped fiber laser

A multi-tap microwave photonic filter is proposed and experimentally demonstrated. The filter is based on a switchable multiple dual-wavelength erbium-doped fiber laser with a narrowband polarization maintaining (PM) Fabry–Perot filter (FPF) as the wavelength selection component. The tunability feature of the filter is also demonstrated through switching of the laser between multiple dual-wavelengths and a normal multiwavelength laser.

New approach to determine the effects of polarization mode dispersion and chromatic dispersion on pulse and RF signals

We present a novel analytical expression relating the output state of polarization (SOP) and the polarization mode dispersion (PMD) vector, including polarization-dependent chromatic dispersion (PCD), in terms of the angle of precession of the output SOP around the PMD vector. We derive a number of new expressions incorporating for the first time this angle of precession. First, a general relation to study the effect of differential group delay, PCD, and chromatic dispersion on pulses of arbitrary shapes is given. From this general relation, we derive expressions for pulse broadening and power penalty for Gaussian pulses. Moreover, a new expression for PMD-induced power fading for single-sideband modulated radio frequency signals is also derived. Measured experimental results are presented to support the derived expressions.

On-line simultaneous monitoring of polarization mode dispersion and chromatic dispersion

We have developed new expressions for power fading and average power fading owing to polarization mode dispersion (PMD) and chromatic dispersion in terms of the angle of precession of the output state of polarization about the PMD vector. Based on these expressions, a simple and novel pilot-tone-based technique for simultaneous monitoring of chromatic dispersion and PMD is proposed. Experimental results demonstrate the effectiveness of the proposed technique; these results agree well with the theoretical analysis.

Novel tunable microwave photonic notch filter with a variable polarization beamsplitter and a Hi-Bi coupler

We demonstrate a tunable microwave-photonic notch filter based on a variable polarization beamsplitter, a Hi-Bi coupler, and a variable time delay line. The configuration is free from the problems of optically coherent interference and chromatic dispersion. An expression for the filter transfer function is derived. Measured results match the calculated results and show a notch rejection greater than 35 dB. The notch frequency is continuously tunable by adjusting the time delay value. The scheme can operate over a wide range of optical carrier frequencies.