Record high 19.125Gb/s real-time end-to-end dual-band optical OFDM (OOFDM) transmission is experimentally demonstrated, for the first time, in a simple electro-absorption modulated laser (EML)-based 25km standard SMF system using intensity modulation and direct detection (IMDD). Adaptively modulated baseband (0-2GHz) and passband (6.125 ± 2GHz) OFDM RF sub-bands, supporting line rates of 10Gb/s and 9.125Gb/s respectively, are independently generated and detected with FPGA-based DSP clocked at only 100MHz and DACs/ADCs operating at sampling speeds as low as 4GS/s. The two OFDM sub-bands are electrically frequency-division-multiplexed (FDM) for intensity modulation of a single optical carrier by an EML. To maximize and balance the signal transmission performance of each sub-band, on-line adaptive features and on-line performance monitoring is fully exploited to optimize key OOFDM transceiver and system parameters, which includes subcarrier characteristics within each individual OFDM sub-band, total and relative sub-band power as well as EML operating conditions. The achieved 19.125Gb/s over 25km SMF OOFDM transmission system has an optical power budget of 13.5dB, and shows almost identical bit error rate (BER) performances for both the baseband and passband signals. In addition, experimental investigations also indicate that the maximum achievable transmission capacity of the present system is mainly determined by the EML frequency chirp-enhanced chromatic dispersion effect, and the passband BER performance is not affected by the two sub-band-induced intermixing effect, which, however, gives a 1.2dB optical power penalty to the baseband signal transmission.
[Show abstract][Hide abstract] ABSTRACT: In this letter, we experimentally demonstrate a complete FPGAs-based real-time point-to-point long-reach (LR) direct-detection optical orthogonal frequency division multiplexing (DDO-OFDM) transmission system using a cost-effective electro-absorption modulated laser (EML) with 1024-point FFT. To our knowledge, it is the so-far reported largest FFT size used in real-time DDO-OFDM system. Based on the system, in an asynchronous way, an adaptively 16-QAM/QPSK/BPSK modulated real-time optical OFDM long-reach transmission has been experimentally demonstrated without sampling frequency offset (SFO) compensation, which is achieved by utilizing the effective symbol timing synchronization and the pilot-aided and linear-interpolated channel estimation scheme. Moreover, the bit-error rate (BER) of below than 1e-3 can be successfully achieved after 150 km standard single mode fiber (SSMF) transmission.
"To address this, the CAP may be implemented by using analog components ,  and using a QAM receiver to decrease its timing jitter sensitivity . Also optical OFDM may be implemented by using multiple bands in the RF domain to parallelize the high speed signal into a few low speed channel signals . "
[Show abstract][Hide abstract] ABSTRACT: For the first time, simulations have been performed to evaluate and compare the link power budget and power dissipation of 100 Gb/s carrierless amplitude and phase modulation-16/64 (CAP-16/64) and 16/64-quadrature amplitude modulation-orthogonal frequency division multiplexing (16/64-QAM-OFDM) systems over feedforward error correction (FEC) enhanced single mode fiber (SMF) links using an 18.6 GHz bandwidth directly modulated laser, for both single channel and two coarse wavelength division multiplexing (CWDM) channel cases. It is shown that single channel CAP-16 and 16-QAM-OFDM links can successfully support transmission over 5 km SMF, with a power dissipation of ~ 2 times that of a 4 × 25 Gb/s NRZ system. Even when the loss of the optical multiplexing/demultiplexing operations is considered, the use of two CWDM channels supports transmission over 5 km SMF with CAP-16 and 16-QAM-OFDM. The CWDM systems do not increase transceiver power dissipation greatly.
[Show abstract][Hide abstract] ABSTRACT: Reflective electro-absorption modulation-intensity modulators (REAM-IMs) are utilized, for the first time, to experimentally demonstrate colorless ONUs in single-fiber-based, bidirectional, intensity-modulation and direct-detection (IMDD), optical OFDM PONs (OOFDM-PONs) incorporating 25km SSMFs and OLT-side-seeded CW optical signals. The colorlessness of the REAM-IMs is characterized, based on which optimum REAM-IM operating conditions are identified. In the aforementioned PON architecture, 10Gb/s colorless upstream transmissions of end-to-end real-time OOFDM signals are successfully achieved for various wavelengths within the entire C-band. Over such a wavelength window, corresponding minimum received optical powers at the FEC limit vary in a range as small as <0.5dB. In addition, experimental measurements also indicate that Rayleigh backscattering imposes a 2.8dB optical power penalty on the 10Gb/s over 25km upstream OOFDM signal transmission. Furthermore, making use of on-line adaptive bit and power loading, a linear trade-off between aggregated signal line rate and optical power budget is observed, which shows that, for the present PON system, a 10% reduction in signal line rate can improve the optical power budget by 2.6dB.
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