Browsing by Author "Kao, Hsuan-Yun"

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850/940-nm VCSEL for optical communication and 3D sensing
(2018-01-01)
Cheng, Chih-Hsien
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Shen, Chih-Chiang
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Kao, Hsuan-Yun
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Hsieh, Dan-Hua
;
Wang, Huai-Yung
This paper is going to review the state-of-the-art of the high-speed 850/940-nm vertical cavity surface emitting laser (VCSEL), discussing the structural design, mode control and the related data transmission performance. InGaAs/AlGaAs multiple quantum well (MQW) was used to increase the differential gain and photon density in VCSEL. The multiple oxide layers and oxide-confined aperture were well designed in VCSEL to decrease the parasitic capacitance and generate single mode (SM) VCSEL. The maximal modulation bandwidth of 30 GHz was achieved with well-designed VCSEL structure. At the end of the paper, other applications of the near-infrared VCSELs are discussed.
Blue Laser Diode Based Free-space Optical Data Transmission elevated to 18 Gbps over 16 m
(2017-09-05)
Huang, Yu-Fang
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Chi, Yu-Chieh
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Kao, Hsuan-Yun
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Tsai, Chen-Ting
;
Wang, Huai-Yung
Up to 18-Gbps direct encoding of blue laser diode (BLD) is demonstrated for free-space data transmission. By reshaping the orthogonal frequency multiplexed (16-QAM OFDM) stream with sidelobe filtering, the raw data rate expedites from 17.2 to 18.4 Gbps. Employing an ultrafast p-i-n photodiode with smaller active area diameter and lower noise equivalent power significantly enlarges the data rate by 1.6 Gbps or upgrades the signal-to-noise ratio (SNR) by 0.2 dB. Replacing the 80-mW BLD with the 120-mW one essentially increases the received SNR by 0.4 dB under enhanced modulation throughput. Reinforcing the beam collimation and collection by increasing the numerical aperture with a plano-convex hyper-hemispherical lens further improves the SNR by 0.6 dB. After optimization, the 16-QAM OFDM data with and without sidelobe filtering are respectively delivered at raw data rates of 16.4 and 18 Gbps with spectral-density usage efficiency as high as 4 bit/s/Hz over 16 m in free space, wherein the BLD carried QAM-OFDM data stream remains its capacity after reformation with sidelobe filtering as the superior inter-carrier-interference immunity reinforces.
Comparison of single-/few-/multi-mode 850 nm VCSELs for optical OFDM transmission
(2017-07-10)
Kao, Hsuan-Yun
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Tsai, Cheng-Ting
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Leong, Shan-Fong
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Peng, Chun-Yen
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Chi, Yu-Chieh
For high-speed optical OFDM transmission applications, a comprehensive comparison of the homemade multi-/few-/single-transverse mode (MM/FM/SM) vertical cavity surface emitting laser (VCSEL) chips is performed. With microwave probe, the direct encoding of pre-leveled 16-QAM OFDM data and transmission over 100-m-long OM4 multi-mode-fiber (MMF) are demonstrated for intra-datacenter applications. The MM VCSEL chip with the largest emission aperture of 11 mu m reveals the highest differential quantum efficiency which provides the highest optical power of 8.67 mW but exhibits the lowest encodable bandwidth of 21 GHz. In contrast, the SM VCSEL chip fabricated with the smallest emission aperture of only 3 mu m provides the highest 3-dB encoding bandwidth up to 23 GHz at a cost of slight heat accumulation. After optimization, with the trade-off set between the receiving signal-to-noise ratio (SNR) and bandwidth, the FM VCSEL chip guarantees the highest optical OFDM transmission bit rate of 96 Gbit/s under back-to-back case with its strongest throughput. Among three VCSEL chips, the SM VCSEL chip with nearly modal-dispersion free feature is treated as the best candidate for carrying the pre-leveled 16-QAM OFDM data over 100-m OM4-MMF with same material structure but exhibits different oxide-layer confined gain cross-sections with one another at 80-Gbit/s with the smallest receiving power penalty of 1.77 dB. (C) 2017 Optical Society of America
CWDM DFBLD Transmitter Module for 10-km Interdata Center With Single-Channel 50-Gbit/s PAM-4 and 62-Gbit/s QAM-OFDM
(2018-02-01)
Kao, Hsuan-Yun
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Su, Zhe-Xian
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Shih, Hsiang-Shun
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Chi, Yu-Chieh
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Tsai, Cheng-Ting
Single-channel 50-Gbit/s 4-level pulse amplitude modulation (PAM-4) and 62-Gbit/s orthogonal frequency division multiplexed quadrature amplitude modulation (QAM-OFDM) direct encoding of an uncooled coarse wavelength division multiplexer (CWDM) 100-Gbit/s distributed feedback laser diodes (DF-BLD) transmitter module at 1310-nm transmitter interdata center transmission over 10-km single-mode fiber (SMF) are demonstrated. To enable preleveled 16-QAM OFDM and PAM-4 data transmissions at 62 and 50 Gbit/s, the 1310-nm channel of the DFBLD CWDM transmitter provides modulation bandwidth of 15 GHz, side-mode suppression ratio of 48 dB, and relative intensity noise of -126 dBc/Hz. For encoding the PAM-4 data, the 1310nm channel of the CWDM DFBLD 100-Gbit/s transmitter achieves transmission capacities of 58 and 50 Gbit/s after BtB and 10-km SMF transmissions, respectively. Instead of supporting the back-to-back 16-QAM OFDM with the transmission at 62 Gbit/s with forward error correction (FEC) certified BER of 3.3x10(-3), such a CWDM 100-Gbit/s DFBLD transmitter module can still maintain its highest data rate capacity to indicate a receiving power penalty of 0.35 dB even after 10-km SMF propagation. This is mainly attributed to the selected channel wavelength of the narrow-linewidth DFBLD, which suffers from extremely low chromatic dispersion and RF fading effect.
Few-Mode 850-nm VCSEL Chip with Direct 16-QAM OFDM Encoding at 80-Gbit/s for 100-m OM4 MMF Link
(2017-01-01)
Kao, Hsuan-Yun
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Tsai, Cheng-Ting
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Pong, Chun-Yen
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Liang, Shan-Fong
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Weng, Zu-Kai
Chip-level direct 16-QAM OFDM encoding of a few-transverse-mode 850-nm Zn-diffused VCSEL is employed to transmit 80-Gbit/s data covering 20-GHz analog bandwidth over 100-m-long OM4 MMF with corresponding BER of 3.3x10(-3).
Few-mode VCSEL chip for 100-Gb/s transmission over 100 m multimode fiber
(2017-10-01)
Kao, Hsuan-Yun
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Chi, Yu-Chieh
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Tsai, Cheng-Ting
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Leong, Shan-Fong
;
Peng, Chun-Yen
A few-mode (FM) vertical cavity surface emitting laser (VCSEL) chip with heavily zinc-diffused contact layer and oxide-confined cross-section is demonstrated for carrying pre-leveled 16-quadrature amplitude modulation orthogonal frequency division multiplexing (QAM-OFDM) data in OM4 multi-mode fiber (MMF) over 100 m for intra-data-center applications. The FM VCSEL chip, which has an oxide-confined emission aperture of 5 mu m, demonstrates high external quantum efficiency, provides an optical power of 2.2 mW at 38 times threshold condition, and exhibits 3 dB direct-modulation bandwidth beyond 22 GHz at a cost of slight heat accumulation. At a DC bias point of 5 mA (22.6I(th)) the FM VCSEL chip, with sufficiently normalized modulation output, supports Baud and data rates of 25 and 100 Gb/s, respectively, with forward error correction (FEC) certifying receiving quality after back-to-back transmission. After passing through 100 m OM4 MMF with a receiving power penalty of 4 dB, the FM VCSEL chip demonstrates FEC-certified transmission of the pre-leveled 16-QAM OFDM data at 92 Gb/s. (C) 2017 Chinese Laser Press
Long-Term Thermal Stability of Single-Mode VCSEL Under 96-Gbit/s OFDM Transmission
(2019-11-01)
Kao, Hsuan-Yun
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Tsai, Cheng-Ting
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Chi, Yu-Chieh
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Peng, Chun-Yen
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Leong, Shan-Fong
Thermal-dependent transmission performance and long-term stability of a single-transverse-mode (SM) vertical-cavity surface-emitting laser (VCSEL) with directly pre-leveled 16quadrature amplitude modulation orthogonal frequency-division multiplexing (16-QAM OFDM) data over 100 m 0M4 multi-mode-fiber (MMF) are demonstrated. Although narrowing the oxide-confined aperture to 3 mu m enables the SM VCSEL with low threshold current of 0.21 mA and high modulation bandwidth of 21.4 GHz, this technology also enlarges the insulating oxide area to accumulate the heat for raising core temperature. This induces a harsh environment as the core temperature persistently increases without dissipation even under the water-cooling control at 20 degrees C. As a result, the SM VCSEL can only guarantee a stable operation for 1.5 h under the encoding of QAM-OFDM data for transmission. After optimization, the SM VCSEL successfully supports a back-to-back transmission capacity as high as 96 Gbit/s. With the assistance of OFDM pre-leveling technique, the 96-Gbit/s QAM-OFDM data transmission is qualified over 100 m OM4 MMF with a receiving power penalty as low as 13 dB.
Modal Linewidth Dependent Transmission Performance of 850-nm VCSELs With Encoding PAM-4 Over 100-m MMF
(2017-10-01)
Kao, Hsuan-Yun
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Chi, Yu-Chieh
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Peng, Chun-Yen
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Leong, Shan-Fong
;
Chang, Chun-Kai
By changing the transverse-mode spectral linewidth of vertical cavity surface emitting lasers (VCSELs) at 850 nm, the directly encoded four-level pulse amplitude modulation data transmission performance over 100-m-long OM4 multimode fiber (MMF) are demonstrated and compared. The multi-mode VCSEL chip with the largest aperture of 11 mu m reveals the widest spectral linewidth and the highest optical power, but provides the smallest modulation bandwidth to support only 44-and 28-Gb/s data rates for back-to-back (BtB) and 100-m OM4 MMF transmission cases, respectively. By shrinking the aperture size to reduce transverse-mode number, the few-mode VCSEL with the strongest throughput power enables a BtB transmission capacity as high as 52 Gb/s. However, its modal dispersion induced after OM4 MMF transmission inevitably degrade the data rate to 32 Gb/s. In contrast, the single-mode VCSEL with the smallest aperture of 3 mu m reveals the highest modulation bandwidth and negligible modal dispersion to show competitive BtB transmission capacity with that of the few-mode VCSEL. In particular, the single-mode VCSEL successfully achieves a data rate of 34 Gb/s with a power penalty as low as 1.4 dB, after 100-m OM4 MMF transmission.
Single-mode VCSEL for pre-emphasis PAM-4 transmission up to 64 Gbit/s over 100-300 m in OM4 MMF
(2018-07-01)
Kao, Hsuan-Yun
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Tsai, Cheng-Ting
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Leong, Shan-Fong
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Peng, Chun-Yen
;
Chi, Yu-Chieh
A 850 nm single-mode vertical cavity surface emitting laser (VCSEL)-based data transmission is demonstrated, enabling four-level pulse amplitude modulation (PAM-4) at 64 Gbit/s over 100-300 m in an OM4 multi-mode fiber (MMF). By optimizing the bias of the single-mode VCSEL with a differential resistance of 159 Omega, the related electrical return loss of -5.7 dB is determined to provide an analog modulation bandwidth of 18.9 GHz. After pre-emphasizing the waveform of the PAM-4 format, the PAM-4 data stream can be successfully delivered by the single-mode VCSEL at 64 Gbit/s under back-to-back and 100 m long OM4 MMF conditions. Lengthening the transmission distance worsens the signal-to-noise ratio (SNR) of PAM-4 data to the FEC criterion, as the waveform pre-emphasis of the PAM-4 data stream inevitably induces spectral power compensation from low to high frequencies. Therefore, increasing the OM4 MMF distance from 200 to 300 m significantly reduces the peak-to-peak amplitude of data to suppress the SNR and reduce the transmission capacity from 52 to 48 Gbit/s. (C) 2018 Chinese Laser Press