Oxide-confined vertical cavity surface emitting lasers (VCSELs) with anti-waveguiding AlAs-rich core presently attract a lot of attention. Anti-waveguiding cavity enables the maximum possible optical ...confinement of the VCSEL mode ("λ/2 design"), increases its oscillator strength and reduces dramatically the optical power accumulated in the VCSEL mesa regions outside the aperture. VCSEL designs are suggested that favor single transverse mode operation. Modeling including current-induced and absorption-induced overheating shows that the preference for the transverse fundamental mode persists up to 10 mA current at 5 µm aperture diameter. Error-free data transmission is realized up to 160 Gb/s in digital-multitone (DMT) format using single-mode anti-waveguiding VCSELs. The approach to single-mode anti-waveguiding VCSELs is extended over a broad spectral range realizing error-free high-speed data transmission at both 850 nm and 910 nm.
In this letter, the experimental operation of a wireless transmission link employing identical LEDs both as transmitter and receiver is demonstrated. The transmitted signal is a simple, two-level ...pulse amplitude modulation. Digital equalization at the receiver is applied to overcome the bandwidth limitation of the link. Transmission throughput exceeding 100 Mbit/s is reported, even if the receiving red LED operates in the photovoltaic mode.
Successful 54 Gbit/s on–off keying (OOK) transmission over 2.2 km of multimode OM4 fibre is demonstrated. The decisive advantages of the single mode over multimode vertical cavity surface emitting ...laser (VCSEL) in transmission experiments are shown.
In the paper, an experimental comparison of pulse amplitude, carrierless amplitude-phase, and discrete multitone modulations is carried in a visible light communications link employing white ...phosphorescent light-emitting diode (LED) as a transmitter. By changing the modulation index, the influence of LED nonlinearity on the performance is studied. The results indicate similar performance of pulse-amplitude modulation (PAM) and carrier-less amplitude-phase (CAP) (with a slight advantage of the former) and substantially worse performance of DMT.
A method of transmission in a single mode fiber below the cut‐off wavelength is proposed. It makes use of the periodic structure of the frequency response of bimodal fiber link and does not require ...optical filtering. The throughputs of around 1 Gbps were obtained for 5 km SM fiber at 850 nm.
By combing Zn-diffusion and oxide-relief apertures with strong detuning (>20 nm) in our demonstrated short-cavity (λ/2) 850-nm vertical-cavity surface-emitting lasers (VCSELs), wide ...electrical-to-optical bandwidth (29-24 GHz), low-differential resistance (~100 Q), and (quasi) single-mode (SM) with reasonable output power (~1.4 mW) performances can be simultaneously achieved. Error-free ON-OFF keying transmission at 54-Gb/s data rate through 1-km OM4 multi-mode fiber can be achieved by using highly SM device with forward error correction and decision feedback equalization techniques. As compared with the reference device with a larger oxide-relief aperture and a multi-mode performance, the SM device exhibits lower bit-error rate (1 × 10 -5 versus 1 × 10 -2 ) at 54 Gb/s. This result indicates that modal dispersion plays more important role in transmission than that of output power does. We benchmark these results to an industrial 50-Gb/s SM VCSEL. It shows a higher bit-error-rate value ~3.5×10 -3 versus ~1.4×10 -4 under the same received optical power.
Fluctuations of the multimode fiber (MMF) frequency response beyond the baseband are observed experimentally when highly coherent light sources are used. This behavior is caused by the variation of ...the mode group powers caused by the relative modal phase fluctuation combined with spatial filtering at elements such as nonideal connectors. The observed effect may have vital influence on subcarrier multiplexing systems operation outside the baseband of the MMF. The effect is investigated both theoretically and experimentally.
The results of studies on fabrication of vertical-cavity surface-emitting 1.55-μm lasers by fusing AlGaAs/GaAs distributed-Bragg-reflector wafers and an active region based on thin In
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As ...quantum wells grown by molecular-beam epitaxy are presented. Lasers with a current aperture diameter of 8 μm exhibit continuous lasing with a threshold current below 1.5 mA, an output optical power of 6 mW, and an efficiency of approximately 22%. Single-mode lasing with a side-mode suppression ratio of 40–45 dB is observed in the entire operating current range. The effective modulation frequency of these lasers is as high as 9 GHz and is limited by the low parasitic cutoff frequency and self-heating.
•Various modulations experimentally compared for SI POF channel.•Maximum bit rates determined for PAM, CAP, and DMT modulations.•Similar performance of PAM and CAP, inferior of DMT.
Investigated was ...the transmission over step index POF that is 50m/100m long with a red DVD laser as a source and a Si p-i-n commercial photo-detector. The maximum bit rates of three modulation formats: PAM, CAP and DMT were sought. Their constellation sizes and symbol rates were varied in order to maximize FEC limited throughputs for each modulation whereas the laser operating point and relevant optical powers were maintained constant for all the modulations. The maximum throughputs were similar for PAM and CAP, namely 3.3/2Gbit/s for PAM, and 3.15/2.1 for CAP for 50/100m fiber, respectively. The bit rates for DMT were 2.65/1.65Gbit/s for the respective lengths of the fiber. We attribute the inferior performance of DMT to its high value of peak to average power ratio.
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