dB Optical Signal-to-noise Ratio Research Articles

Novel Rx IQ mismatch compensation considering laser phase noise for CO-OFDM system

In this paper, a novel compensation scheme for receiver (Rx) in-phase/quadrature (IQ) mismatch is proposed in coherent optical orthogonal frequency division multiplexing (CO-OFDM) system in the presence of laser phase noise. In this scheme, laser phase noise and channel distortion were combined as a new channel transfer factor, the IQ mismatch factor and initial channel transfer factor can be estimated independently based on the relationship of IQ mismatch factors. And the channel transfer factor can be updated on a symbol-by-symbol basis which retrieves an estimation of the phase noise value by extracting and averaging the phase drift of all OFDM sub-channels. Numerical results indicate that when the phase and amplitude mismatch are 10° and 2dB respectively, a 1.6dB optical signal-to noise ratio is improved at laser linewidth of 60kHz. Furthermore, the complexity of the proposed method is analyzed in terms of the number of required complex multiplications per bit.

High signal-to-noise ratio, single-frequency 2 μm Brillouin fiber laser.

A high optical signal-to-noise ratio (OSNR) single-frequency 2 μm Brillouin fiber laser (BFL) with watt-level output and high transfer efficiency is demonstrated for the first time to the best of our knowledge. The Brillouin pump is constructed with a two-stage thulium-doped fiber amplifier (TDFA) seeded by a 2 μm laser diode, providing 4.02 W average power with 1 MHz linewidth. Using an optimized length of 14 m for the Brillouin ring cavity, the BFL works stably in single-mode region with 8 kHz linewidth because of the linewidth narrowing effect. The transfer efficiency is 51% with 1.08 W output power and 62 dB OSNR for 3.22 W pump power.

Analysis of dispersion-enhanced phase noise in

We show that dispersion-enhanced phase noise (DEPN) induces performance degradations in both conventional CO-OFDM systems and reduced-guard-interval (RGI) CO-OFDM systems employing RF-pilot phase compensation. After analytically studying DEPN, we show that DEPN causes a 2 to 6 dB optical signal-to-noise ratio (OSNR) penalty at transmission distances of 3200 km and 1600 km for 28 and 56 Gbaud QPSK systems, respectively, using lasers with 2 MHz linewidths. At such distances, DEPN reduces the linewidth tolerance at 1 dB OSNR penalty to 250-500 kHz while in the back-to-back case the tolerance is 1-3 MHz for both systems. When fiber nonlinearity is included, we observe similar performance degradations.

RoF transport systems with OSNR enhanced multi-band optical carrier generator

A combination of an economic multi-band optical carrier generator and a novel optical signal to noise ratio (OSNR) enhancement circuit is proposed and demonstrated for radio over fiber (RoF) transport systems. Different from normal RoF transport systems which a central station (CS) needs multiple dedicate wavelength laser diodes (LDs) to support various base stations (BSs), the proposed scheme can employ a single LD to provide multiple optical carriers for various BSs. To verify this scheme, 8 coherent optical carriers are firstly generated using a single LD and a local oscillator (LO). Subsequently, their OSNR values are optimized by the developed OSNR enhancement circuit. An up to 15 dB OSNR enlargement in those optical carriers is experimentally achieved. To demonstrate the practice of the proposal, a pair of those optical carriers is employed to experimentally achieve frequency up-conversion process in a RoF transport system. Clear eye diagram and error free transmission reveal that with a proper carrier selector the proposed scheme can be employed to support multiple RoF transmissions. Furthermore, this proposal also presents a high possibility to achieve 60 GHz RoF transmission using a 10 GHz LO, a LD and a low frequency external modulator.

Duty-cycle-division-multiplexing: Bit error rate estimation and performance evaluation

An improved estimation of bit-error-rate (BER) for electrically multiplexed duty-cycle division multiplexing (E-DCDM), which is based on the probability of error, is presented. Performance of 3 × 10 Gbit/s E-DCDM is investigated in terms of optical signal-to-noise ratio (OSNR) and dispersion tolerance. This technique requires 29.4 dB OSNR and can tolerate ±96 ps/nm chromatic dispersion for the worst user.

Electronic dispersion compensation using full optical-field reconstruction in 10Gbit/s OOK based systems

We investigate the design of electronic dispersion compensation (EDC) using full optical-field reconstruction in 10Gbit/s on-off keyed transmission systems limited by optical signal-to-noise ratio (OSNR). By effectively suppressing the impairment due to low-frequency component amplification in phase reconstruction, properly designing the transmission system configuration to combat fiber nonlinearity, and successfully reducing the vulnerability to thermal noise, a 4.8dB OSNR margin can be achieved for 2160km single-mode fiber transmission without any optical dispersion compensation. We also investigate the performance sensitivity of the scheme to various system parameters, and propose a novel method to greatly enhance the tolerance to differential phase misalignment of the asymmetric Mach-Zehnder interferometer. This numerical study provides important design guidelines which will enable full optical-field EDC to become a cost-effective dispersion compensation solution for future transparent optical networks.