Optical Phase Diversity Research Articles

Seamless Digital Wireless-Photonic Receiver With Optical Phase Diversity

Seamless Digital Wireless-Photonic Receiver With Optical Phase Diversity

Ultra-fast full-field optical characterization of CW lasers based on optical frequency comb, wavelength-to-time mapping and phase-diversity.

Optical frequency comb (OFC), a periodic optical pulse train in time domain, has been widely employed to measure optical frequency due to its equidistant modes in the frequency domain. Here, we propose and demonstrate a novel optical spectrum analyzer for CW lasers based on stretching the OFC in a dispersive element and mapping the frequency comb into the time domain. The optical spectrum analyzer also provides instantaneous full-field (wavelength, amplitude and phase) optical characterization capability by combining with optical phase-diversity technology. Experimental results show that we successfully trace the evolution of modulated lasers with a measurement speed of ∼51 MHz (related to the pulse repetition of the OFC) and a high spectral resolution of ∼21 pm. Thanks to the use of wavelength-to-time mapping and OFC, the single channel measurement range of the proposed system can reach ∼10 nm, which breaks the restriction of the bandwidth of photodetector.

Integrated Optical Six-Port Reflectometer in Silicon on Insulator

The six-port reflectometer technique enables simple and accurate measurement of optical reflection coefficients in both magnitude and phase. The reflection coefficient is computed from four power measurements of linear combinations of the waves incident and reflected from the device under test. While the six-port technique is very successful at microwave frequencies and conceptually related to coherent optical phase diversity receivers, no optical implementations have been reported so far. In this paper, we present an experimental characterization of an optical six-port reflectometer composed of three multimode interference couplers, fabricated with a single etch step in silicon on insulator. Measurements are performed using a novel technique with a simple setup. The six-port combines the incident and reflected waves with magnitude and phase errors less than plusmn0.5 dB and plusmn6deg in the 1485-1575 nm band.

Two-Dimensional Spatio-Temporal Signal Processing for Dispersion Compensation in Time-Stretched ADC

Time-stretched analog-to-digital converters (ADCs) have offered revolutionary enhancements in the performance of electronic converters by reducing the signal bandwidth prior to digitization. An inherent limitation of the time-stretched ADC is the frequency-selective response of the optical system that reduces the effective number of bits for ultrawideband signals. This paper proposes a solution based on spatio-temporal digital processing. The digital algorithm exploits the optical phase diversity to create a flat RF frequency response, even when the system's transfer function included deep nulls within the signal spectrum. For a 10times time-stretch factor with a 10-GHz input signal, simulations show that the proposed solution increases the overall achievable signal-to-noise-and-distortion ratio to 52 dB in the presence of linear distortions. The proposed filter can be used to mitigate the dispersion penalty in other fiber optic applications as well.

Balanced Optical Phase Diversity Receivers for Coherence Multiplexing

Coherence multiplexing (CM) is a specific form of CDMA that is particularly suitable for optical communication systems for medium data rates and small distances. By virtue of its potentially simple implementation, it is particularly useful for bridging the last mile to the subscribers, which is an issue that is receiving considerable attention in optical communication research nowadays. The receivers in coherence multiplex systems published so far were all based on either self-homodyne or self-heterodyne detection. Both solutions are rather complicated, and therefore, expensive. In this paper, a new CM receiver concept is proposed, based on optical phase diversity detection. Theoretical performance results are derived for several modulation formats and receiver structures.

A Novel Study on the Performance of a {3 x 3} Optical Phase Diversity FSK Receiver

The performance of {3 x 3} optical phase diversity FSK receivers using delay-and-multiplying discriminator is analyzed by means of Gaussian and non-Gaussian methods, respectively. Non-Gaussian method utilizes the characteristic function to derive PDF of the noisy output. Shot, thermal, intensity. and phase noises are all considered and modeled as system imperfections. The formulation results show that the intensity noises are cancelled out and have no effect on the receiver performance. The numerical results show that there is a closed match between Gaussian and non-Gaussian analyses when thc deviation-delay product f d τ is in the vicinity of 0.25. If this product is far away from 0.25, the performance is greatly degraded as seen from the non-Gaussian calculations and the deviation due to Gaussian approximation also becomes very significant.

Calculating the performance of optical CPFSK phase diversity receivers

Numerical method for efficiently computing the performance of continuous phase frequency shift keying (CPFSK) is presented. The receiver uses a phase diversity technique with a delay-and-multiply frequency discriminator to recover the phase of the optical signal. The moment generating function (MGF) of the discriminator is derived and used in the calculation of bit error rate (BER). The results of numerical integration show that the receiver output is far from Gaussian. Exact mean and variance are derived for the Gaussian approximation (GA). The effects of laser linewidth, filter bandwidth, and shot noise correlation are all considered. >

A Comparison of Performance between (2 × 2) and (3 × 3) Optical Phase Diversity FSK Receivers Using Delay-and-Multiplying Discriminator

The performance {2 × 2} and {3 × 3} optical phase diversity FSK receivers using delay-and-multiplying discriminator is analyzed, respectively. Given data rate, frequency deviation, laser linewidth, relative intensity noise (RIN), and thermal noise, we can obtain the received signal power (sensitivity) with respect to a given local oscillator power to achieve a specified BER. Numerical results with system parameters given in [1] show that the optimal local oscillator (L.O.) power of a {2 × 2} receiver is −6.5 dBm, −14 dBm, and −19 dBm for RIN = −150 dB/Hz, −135 dB/Hz, and −125 dB/Hz, respectively, when the thermal noise is 9.10 −24 A 2 /Hz

Gaussian and exact analyses on the effect of local oscillator intensity noise in optical phase diversity FSK receiver

The impact of local oscillator intensity noise on the performance of an optical phase diversity FSK receiver using a delay-and-multiplying discriminator is analyzed for both Gaussian approximation and exact non-Gaussian statistics. The bit error rate (BER) is expressed in terms of Q-function using Gaussian approximation. Also, an exact equation for BER is derived by a non-Gaussian approach. Given data rate, frequency deviation, discriminator delay, composite laser linewidth, bandwidth ratio of pre- and post-detection lowpass filters, local oscillator relative intensity noise (RIN), and receiver thermal noise, the received signal power (sensitivity) can be calculated with respect to given local oscillator power for a specified BER. Both Gaussian and non-Gaussian numerical results show that there exists an optimal local oscillator power to achieve maximum sensitivity for RIN -150 dB/Hz, -135 dB/Hz, and -125 dB/Hz, respectively, at a BER of 10/sup -9/ The deviation of sensitivity between Gaussian and non-Gaussian (exact) results is shown to be within 1 dB for the illustrated examples, when the product of frequency deviation and discriminator delay is equal to 0.25. If this product is far away from 0.25, the performance is greatly degraded as seen from the exact calculations and the deviation due to Gaussian approximation also becomes very significant. >

Theoretical analysis of phase diversity optical homodyne receiver with FSK demodulation

A detailed analysis of optical coherent phase diversity single-filtered and dual-filtered frequency-shift keying (FSK) receivers corrupted by shot and phase noise is presented. With delay and cross-product detection, the effect of various parameters, including bandwidths of filters, delay time, frequency deviation and noises, are investigated. The tolerance of phase noise is quite large, when small time delay in the demodulator and appropriately large frequency deviation is selected. It is also shown that there exists an optimal bandwidth for the first filter in the dual-filtered FSK receiver. For a total linewidth equal to half of the bit rate, the power penalty incurred (at BER=10/sup -9/) is 1.92 dB when the modulation index is 4, provided that an optimal filter bandwidth and a frequency deviation-delay product of 0.25 are used.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Impact of local oscillator intensity noise on the performance of the optical phase-diversity fsk receiver using delay-and-multiplying discriminator

The impact of local oscillator intensity noise on the performance of an optical phase-diversity FSK receiver using a delay-and-multiplying discriminator is analyzed. Given the data rate, frequency deviation, laser linewidth, RIN noise, and thermal noise, we can obtain the minimum received signal power together with the corresponding optimal local oscillator power to achieve the required BER. Numerical results with system parameters given in [1] show that (PL)opt is -1.46 dBm for RIN = -160 dB/Hz and -6.4 dBm for RIN = -150 dB/Hz when the thermal noise is 9 × 10−24 A2/Hz.

Performance Analysis of Optical FSK Phase Diversity Receivers in the Presence of Thermal Noise

Performance Analysis of Optical FSK Phase Diversity Receivers in the Presence of Thermal Noise

Sensitivity degradation of an optical (2*2) and a (3*3) phase diversity ASK receiver due to gain imbalance and nonideal phase relations of the optical hybrid

The sensitivity penalty due to phase and gain imbalance for a (2*2) and a (3*3) optical homodyne phase diversity amplitude-shift keying (ASK) receiver is investigated for the shot-noise-limited case. It is shown that both types of imbalance lead to a time varying character of the bit error rate (BER) types of imbalance and the phase mismatch. The calculation of the BER is performed as a function of the threshold value. It is shown that for an optimized threshold value, the phase diversity ASK receivers can tolerate rather large amounts of gain imbalance, namely approximately +or-10%, and a phase mismatch of approximately +or-10 degrees for the (2*2) receiver and approximately not=15 degrees for the (3*3) receiver without an excessive sensitivity degradation (<2 dB).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Power Penalty due to Intersymbol Interference in Optical Phase Diversity FSK Systems

Power Penalty due to Intersymbol Interference in Optical Phase Diversity FSK Systems

Digital demodulator for optical FSK signals

This letter presents a novel FSK-demodulator for optical phase diversity receivers. It is based on a digital flip-flop and is shown to have a sensitivity of about 3 dB below that of a delay and multiply demodulator. The concept is a step towards a fully integrated low-cost FSK receiver.

Sensitivity Comparison of Coherent Optical Heterodyne, Phase Diversity, and Polarization Diversity Receivers

Article Sensitivity Comparison of Coherent Optical Heterodyne, Phase Diversity, and Polarization Diversity Receivers was published on March 1, 1989 in the journal Journal of Optical Communications (volume 10, issue 1).

Performance Analysis of Optical Phase Diversity FSK Receiver Using Delay-and-Multiplying Discriminators

Article Performance Analysis of Optical Phase Diversity FSK Receiver Using Delay-and-Multiplying Discriminators was published on September 1, 1989 in the journal Journal of Optical Communications (volume 10, issue 3).