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Blue Laser Diode Based Free-space Optical Data Transmission elevated to 18 Gbps over 16 m
Yu-Fang Huang1, Yu-Chieh Chi1, Hsuan-Yun Kao1
1Graduate Institute of Photonics and Optoelectronics, and the Department of Electrical Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, R.O.C., Taiwan.
Scientific Reports
|September 7, 2017
Summary
This study demonstrates 18-Gbps free-space data transmission using a blue laser diode (BLD). Optimizations in modulation, photodetection, and beam collimation significantly boosted data rates and signal quality for wireless optical communication.
Area of Science:
- Optical Communications
- Free-Space Optics
- Wireless Data Transmission
Background:
- High-speed free-space optical communication is crucial for next-generation networks.
- Blue laser diodes (BLDs) offer potential for high-bandwidth optical links.
- Challenges include achieving high data rates and maintaining signal integrity over distance.
Purpose of the Study:
- To demonstrate direct encoding of high-speed data onto a blue laser diode for free-space transmission.
- To investigate methods for enhancing data rates and signal-to-noise ratio (SNR).
- To evaluate the effectiveness of modulation techniques and optical component optimization.
Main Methods:
- Direct encoding of a 16-quadrature amplitude modulation orthogonal frequency-division multiplexing (16-QAM OFDM) stream onto a BLD.
- Sidelobe filtering to reshape the OFDM stream and improve data rate.
- Utilizing an ultrafast p-i-n photodiode with optimized parameters.
- Employing a higher-power BLD (120-mW) and optimizing beam collimation with a plano-convex hyper-hemispherical lens.
Main Results:
- Achieved a raw data rate of up to 18 Gbps for free-space data transmission.
- Sidelobe filtering increased the data rate from 17.2 to 18.4 Gbps.
- Photodiode optimization improved data rate by 1.6 Gbps or SNR by 0.2 dB.
- Higher power BLD and improved beam collimation further enhanced SNR by 0.4 dB and 0.6 dB, respectively.
- Demonstrated spectral-density usage efficiency of 4 bit/s/Hz over 16 m.
Conclusions:
- Direct encoding of 16-QAM OFDM data onto BLDs is feasible for high-speed free-space communication.
- Modulation reshaping, advanced photodetection, and optimized beam optics are key to achieving high data rates and SNR.
- Sidelobe filtering enhances inter-carrier-interference immunity, maintaining data stream capacity.
