Modulation Bandwidth Of LEDs Research Articles

A Systematic Review on Non-Orthogonal Multiple Access (NOMA) Based on Visible Light Communication for Intelligent Transportation Systems

Non-Orthogonal Multiple Access (NOMA) is a cutting-edge technology that permits several users to use the same frequency resources and transfer data at once. Visible light communication also known as VLC, is an innovative technology that offers access to an unoccupied spectrum, enables fast data transmission speeds, thereby making it a complementary addition to current radio frequency technology. Although VLC has its advantages, it also comes with some downsides. One major issue is the modulation bandwidth of LEDs, which can be quite challenging when creating high speed VLC systems. Non-orthogonal multiple access (NOMA), particularly power-domain NOMA (PD-NOMA), has become a viable multiple access approach, ensuring sufficient bandwidth allocation for VLC systems. This study delves into multiple access techniques in VLC systems, in particular NOMA, and discusses its fundamental principles, key ideas and practical implementations like vehicular communication. It also addresses the associated hurdles, such as ensuring equitable distribution of optical power among users, leveraging MIMO technology, and grappling with LED nonlinearity issues. In summary, we underscore the significance of utilizing NOMA-VLC technology to enhance wireless communication systems and optimize spectral efficiency.

室内VLC白光LED调制带宽拓展

室内VLC白光LED调制带宽拓展

VLC系统偏置电流对LED调制带宽的影响分析

VLC系统偏置电流对LED调制带宽的影响分析

Impedance, modulation response and equivalent-circuit of 650 nm surface emitting type light-emitting diode for POF data-links

The basic electrical equivalent circuit of an AlGaInP based 650 nm ring-LED proposed for plastic-optical fiber data-links is derived. The LED's modulation bandwidth is found to be 65 MHz at a link average driving bias current of 35 mA. The LED's modulation response is measured and shows an open-eye diagram for 156 Mbps non-return-to-zero (NRZ), pseudo-random signals with and without a peaking circuit, respectively.

Extension of the modulation bandwidth of LEDs by pole cancellation

It is shown that the dominant pole due to the small-signal equivalent circuit of an LED can be nullified by a transmission zero provided by the source impedance so that the light intensity modulation may have a maximally flat frequency response and the 3dB modulation bandwidth may be extended well beyond the limit set by the charge recombination time-constant of the device. Computer simulation has confirmed that the series parasitic inductance and resistance of the device play an important role in limiting the bandwidth. The pole cancellation method is equally applicable to circuits using an array of identical devices. In the case where the devices in an array have different poles, the compensated response is no longer maximally flat but is significantly broader than the uncompensated one.

High Bit Rate Fibre-Optic Transmission Using Bipolar Pulsing and Duo-Binary Signalling

Schemes for high bit rate transmission of fibre-optic signal using LEDS with bipolar pulsing and duo-binary signalling have been discussed. The reverse pulsing together with preshaping of driving pulses has been found to increase the LED modulation bandwidth by a factor of four while with duo-binary signalling the bit-rate can be increased by a factor of two with 4–5 dB power penalty. A combination of the two techniques can thus lead to significant improvement in the bit-rate of transmission.