RESUMEN
The use of Alamouti-coded polarization-time block code (A-PTBC) in combination with a simple single polarization coherent receiver enables phase-diverse coherent detection without any optical polarization tracking. However, applying this technique to high-speed single-carrier systems is not straightforward, as it requires specialized digital signal processing (DSP) algorithms for data recovery, which increases DSP complexity. In this paper, we propose a novel Alamouti-coded coherent algorithm designed to significantly reduce the complexity of the receiver DSP for data recovery. The proposed algorithm achieves the comparable performance to the conventional algorithm but requires only half the number of necessary equalizers for data recovery. We validate its performance through simulations and also experimentally demonstrate a 100 Gb/s 16-quadrature amplitude modulation (QAM) single-carrier coherent system employed the single-polarization coherent receiver over 20â km of standard single-mode fiber (SMF). Through the performance verification, the coherent system with the proposed algorithm exhibits performance comparable to that of the conventional Alamouti-coded coherent system and achieves a power budget of 34â dB when the transmit launch power is set to 7 dBm at a Bit Error Rate (BER) of 1 × 10-2 for 0-20â km fiber transmission.
RESUMEN
All-fiber 6-mode multiplexer composed of two consecutive LP11-mode selective couplers (MSC), two LP21-MSCs and an LP02-MSC is fully characterized by wavelength-swept interferometer technique. The MSCs are fabricated by polished-type fiber couplers coupling LP01 mode of a single mode fiber into a higher-order mode of a few mode fiber. A pair of the mode multiplexers has minimum mode dependent loss of 4 dB and high mode group selectivity of over 15 dB. Mode division multiplexed transmission enabled by the all-fiber mode multiplexers is demonstrated over fiber spans of 117 km employing an in-line multi-mode optical amplifier. 6 modes of 120 Gb/s dual polarization quadrature phase shift keying signals combined with 30 wavelength channels are successfully transmitted.
RESUMEN
We propose all-fiber mode multiplexer composed of two consecutive LP11 mode selective couplers that allows for the multiplexing of LP01 mode and two-fold degenerate LP11 modes. We demonstrate WDM transmission of 32 wavelength channels with 100 GHz spacing, each carrying 3 modes of 120 Gb/s polarization division multiplexed quadrature phase shifted keying (PDM-QPSK) signal, over 560 km of few-mode fiber (FMF). Long distance transmission is achieved by 6×6 multiple-input multiple-output digital signal processing and modal differential group delay compensated link of FMF. The all-fiber mode multiplexer has considerable potential to be used in mode- and wavelength-division multiplexed transmission.
RESUMEN
Mode division multiplexed optical transmission enabled by all-fiber mode multiplexer is investigated. The proposed all-fiber mode multiplexer is composed of consecutive mode selective couplers. It multiplexes or demultiplexes LP01, LP11, LP21, and LP02 modes simultaneously. We demonstrate successful transmission of three spatial modes with 120 Gb/s PDM-QPSK signals over 15 km of four mode fiber by using 6x6 MIMO digital signal processing.
RESUMEN
When optical transceivers employing in-phase and quadrature (IQ) modulators and demodulator are used in real transmission systems, it is very important to search optimum bias points and to prevent bias drift from their optimal points due to of temperature variation, stress, or device aging. We demonstrate a simple and cost-effective automatic bias control scheme for optical IQ modulator and demodulator based on RF power and peak voltage detection. The principle of control scheme and effects of bias voltage on monitoring parameters are presented. The dynamic performance of the control scheme, effects of optical signal-to-noise ratio (OSNR) of signal, and effects of temperature variation are also evaluated. For the evaluation of bias control scheme at real-environment, we implement the automatic bias control scheme in 112 Gb/s dual carrier-differential QPSK (DC-DQPSK) transceiver, and investigate its long-term stability performances in a field transmission experiment over 797-km of installed fiber and ROADM.
RESUMEN
We demonstrate a mitigation of fiber nonlinearity based on µ-law companding transform in coherent optical OFDM transmissions. High peak-to-average power ratio (PAPR) increases fiber nonlinear impairments caused by the Kerr effect in optical fiber. The µ-law companding modifies amplitude profile of OFDM signal with time domain signal processing, which reduces high PAPR of OFDM signal. The effects of companding parameter on noise enhancement and PAPR variation are presented. The impacts of companding transform on system performances are evaluated in a single polarization system as well as polarization multiplexed system. The resolution of analog-to-digital converter (ADC), dispersion map of transmission link, and launch power tolerance are also considered. The results of bit-error-rate (BER) measurements show that the µ-law companding improves OSNR margin over 5.5 dB after transmission of 1,040 km over SMF.
RESUMEN
Digital symbol synchronization of optical binary phase shift keying signals is experimentally demonstrated. Algorithm of timing error feedback is proposed for coherent intradyne reception. The feedback loop operates stable in the range of symbol rate, 9.7 approximately 10.3 GSymbol/s with 20 GSampling/s at relatively high bit error rate of approximately 2x10(-2).
