Sub-cycle QAM modulation for VCSEL-based optical fiber links.

QAM modulation utilizing subcarrier frequency lower than the symbol rate is both theoretically and experimentally investigated. High spectral efficiency and concentration of power in low frequencies make sub-cycle QAM signals attractive for optical fiber links with direct modulated light sources. Real-time generated 10-Gbps 4-level QAM signal in a 7.5-GHz bandwidth utilizing subcarrier frequency at a half symbol rate was successfully transmitted over 20-km SMF using an un-cooled 1.5-µm VCSEL. Only 2.5-dB fiber transmission power penalty was observed with no equalization applied.

2x2 MIMO-OFDM Gigabit fiber-wireless access system based on polarization division multiplexed WDM-PON.

We propose a spectral efficient radio over wavelength division multiplexed passive optical network (WDM-PON) system by combining optical polarization division multiplexing (PDM) and wireless multiple input multiple output (MIMO) spatial multiplexing techniques. In our experiment, a training-based zero forcing (ZF) channel estimation algorithm is designed to compensate the polarization rotation and wireless multipath fading. A 797 Mb/s net data rate QPSK-OFDM signal with error free (<1 × 10(5)) performance and a 1.59 Gb/s net data rate 16QAM-OFDM signal with BER performance of 1.2 × 10(2) are achieved after transmission of 22.8 km single mode fiber followed by 3 m and 1 m air distances, respectively.

MIMO-OFDM WDM PON with DM-VCSEL for femtocells application.

We report on experimental demonstration of 2x2 MIMO-OFDM 5.6-GHz radio over fiber signaling over 20 km WDM-PON with directly modulated (DM) VCSELs for femtocells application. MIMO-OFDM algorithms effectively compensate for impairments in the wireless link. Error-free signal demodulation of 64 subcarrier 4-QAM signals modulated at 198.5 Mb/s net data rate is achieved after fiber and 2 m indoor wireless transmission. We report BER of 7x10(-3) at the receiver for 16-QAM signals modulated at 397 Mb/s after 1 m of wireless transmission. Performance dependence on different wireless transmission path lengths, antenna separation, and number of subcarriers have been investigated.

Carrierless amplitude phase modulation of VCSEL with 4 bit/s/Hz spectral efficiency for use in WDM-PON.

We experimentally demonstrate successful performance of VCSEL-based WDM link supporting advanced 16-level carrierless amplitude/phase modulation up to 1.25 Gbps, over 26 km SSMF with spectral efficiency of 4 bit/s/Hz for application in high capacity PONs.

All-VCSEL based digital coherent detection link for multi Gbit/s WDM passive optical networks.

We report on experimental demonstration of a digital coherent detection link fully based on vertical cavity surface emitting lasers (VCSELs) for the transmitter as well as for the local oscillator light source at the receiver side. We demonstrate operation at 5 Gbps at a 1550 nm wavelength with record receiver sensitivity of -36 dBm after transmission over 40 km standard single mode fiber. Digital signal processing compensates for frequency offset between the transmitter and the local oscillator VCSELs, and for chromatic dispersion. This system allows for uncooled VCSEL operation and fully passive fiber transmission with no use of optical amplification or optical dispersion compensation. The proposed system demonstrates the potential of multi-gigabit coherent passive optical networks with extended reach and increased capacity. Moreover, this is, to the best of our knowledge, the first demonstration of coherent optical transmission systems using a low-cost VCSEL as the local oscillator as well as for the transmitter.

4 Gbps impulse radio (IR) ultra-wideband (UWB) transmission over 100 meters multi mode fiber with 4 meters wireless transmission.

We present experimental demonstrations of in-building impulse radio (IR) ultra-wideband (UWB) link consisting of 100 m multi mode fiber (MMF) and 4 m wireless transmission at a record 4 Gbps, and a record 8 m wireless transmission at 2.5 Gbps. A directly modulated vertical cavity surface emitting laser (VCSEL) was used for the generation of the optical signal. 8 m at 2.5 Gbps corresponds to a bit rate--distance product of 20; the highest yet reported for wireless IR-UWB transmission.