LED receiver impedance and its effects on LED-LED visible light communications

TL;DR

This paper investigates how the AC impedance spectrum of LEDs as photodetectors varies with received optical power, impacting bandwidth and SNR in LED-LED visible light communication links.

Contribution

It experimentally demonstrates the power-dependent impedance of LEDs and models it with a modified dispersive carrier transport model, revealing effects on communication performance.

Findings

Impedance spectrum depends heavily on received optical power.

Bandwidth decreases as received optical power increases.

Trade-off exists between bandwidth and SNR affecting modulation choices.

Abstract

This paper experimentally demonstrates that the AC impedance spectrum of the LED as a photodetector heavily depends on the received optical power, which may cause the impedance mismatch between the LED and the post trans-impedance amplifier. The optical power dependent impedance of the LED is well fitted by a modified dispersive carrier transport model for inorganic semiconductors. The bandwidth of the LED-LED visible light communication link is further shown to decrease with the optical power received by the LED. This leads to a trade-off between link bandwidth and SNR, and consequently affects the choice of the proper dada modulation scheme.