Browsing by Author "Chi, Kai-Lun"

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850 nm Vertical-Cavity Surface-Emitting Laser Arrays With Enhanced High-Speed Transmission Performance Over a Standard Multimode Fiber
(2017-08-01)
Yen, Jia-Liang
;
Chen, Xin-Nan
;
Chi, Kai-Lun
;
Chen, Jason
;
Shi, Jin-Wei
The functionality of novel parallel and series highspeed vertical-cavity surface-emitting laser (VCSEL) arrays, which can greatly relax the tradeoff between output power and modulation speed, is demonstrated. Both types of array structure allow improvement in the output power with no degradation in their maximum modulation speed as compared to a single reference unit. The observed invariant electrical-optical bandwidth shown for these array structures is mainly due to the effective reduction of the differential resistance and parasitic capacitance, arising from the Zn-diffusion and oxide-relief apertures fabricated in the VCSEL unit. This in turn minimizes the degradation in the RC-limited bandwidth with the VCSEL arrays. Furthermore, the dense packing of single VCSELs, with Zn-diffusion apertures for optical mode control, minimizes the coupling loss between the output from the array into a standard multimode fiber (MMF). Compared with the single VCSEL unit, the parallel VCSEL array shows a significant enhancement in transmission performance over a standard OM4 MMF, which includes a larger eye margin, a higher signal-to-noise ratio, as well as a higher error-free data rate (48 versus 44 Gbit/sec). The device modeling technique is used to perform device analysis. From the results we can conclude that the improvement with the parallel array is because the value of the internal impedance is closer to the 50-Omega signal source, which minimizes the microwave reflection induced timing jitter in the eye-patterns.
850-nm VCSELs With p-Type delta-Doping in the Active Layers for Improved High-Speed and High-Temperature Performance
(2016-11)
Chi, Kai-Lun
;
Hsieh, Dan-Hua
;
Yen, Jia-Liang
;
Chen, Xin-Nan
;
Chen, Jason (Jyehong)
In this paper, we study the influence of p-type modulation doping on the dynamic/static performance of highspeed 850-nm VCSELs with highly strained multiple quantum wells. The studied device structure has a 3/2 lambda asymmetric cavity design, which can let the internal transit time of injected carriers be as short as that of 1/2 lambda cavity design and further improve its performance in terms of speed and output power for high single-mode operation. Our proposed VCSEL structure with p-type doping shows superior modulation speed with an output power comparable with that of the un-doped reference device under room temperature operation. Furthermore, when the operating temperature reaches 85 degrees C, there is a significant improvement in both the modulation speed and maximum power of the p-doped structures. According to our simulation, this can be attributed to the change in the quasi-Fermi levels of the injected carriers after the addition of p-doping in the active layers, which minimizes the electron leakage under high-temperature operation.
93% Complexity Reduction of Volterra Nonlinear Equalizer by l(1)-Regularization for 112-Gbps PAM-4 850-nm VCSEL Optical Interconnect
(2018-01-01)
Huang, Wan-Jou
;
Chang, Wei-Fan
;
Wei, Chia-Chien
;
Liu, Jun-Jie
;
Chen, Yi-Ching
We successfully transmit a 112-Gbps PAM-4 signal over 200-m OM4 fiber using 850-nm VCSEL and Volterra filter. Adopting l(1)-regularization can reduce 93% of computation complexity of Volterra filter at the KP4 FEC limit.
Bandwidth Enhancement Equalization Enabling a 40-Gbps PAM4 Transmission via a 9.5-GHz Photoreceiver
(2016)
Liu, Jun-Jie
;
Wei, Chia-Chien
;
Tzu, Ta-Ching
;
Chuang, Chun-Yen
;
Chi, Kai-Lun
We demonstrate a 40-Gbps PAM4 optical system by employing a photoreceiver with bandwidth of only 9.5 GHz. Following 100 m multimode fiber, the BER of l. 8 x 10(-4) and 1.2 x 10(-4) after FFE and DFE equalizations are successfully achieved
Employing Deep Neural Network for High Speed 4-PAM Optical Interconnect
(2017-01-01)
Chuang, Chun-Yen
;
Wei, Chia-Chien
;
Lin, Tien-Chien
;
Chi, Kai-Lun
;
Liu, Li-Chun
We implement a deep neural network (DNN) to attain a 64-Gbps 4-PAM, 4-km MMF link by using 850-nm VCSEL, with BER of 4.41 x 10(-5). The data-rate-distance product achieves recorded high of 256-Gbps.km for Inter-data center applications.
Energy Efficient 850 nm Vertical-Cavity Surface-Emitting Lasers with Extremely Low Driving-Current Density for > 40 Gbit/sec Error-Free Transmissions from RT to 85 degrees C
(2015)
Chi, Kai-Lun
;
Jiang, Jia-Wei
;
Yen, Jia-Liang
;
Lu, I-Cheng
;
Kuo, H. -C.
850nm VCSELs with record-low driving-current-density (8kA/cm(2)) small resistance (6012), wide-bandwidth (26GHz), and small energy-to-data-rate ratio (228fJ/bit; 3.5mA) for >41Gbit/sec error-free transmission over 100 (2) meter OM4 fiber at room-temperature (85 degrees C) have been demonstrated. (C) 2014 Optical Society of America
High Bit-Rate Distance Product of 128 Gbps.km 4-PAM Transmission over 2-km 0M4 fiber Using an 850-nm VCSEL and a Volterra Nonlinear Equalizer
(2017-01-01)
Liu, Jun-Jie
;
Chi, Kai-Lun
;
Wei, Chia-Chien
;
Lin, Tien-Chien
;
Chuang, Chun-Yen
We successfully demonstrate a 64-Gbps 4-PAM transmission over 2-kin OM4 fiber incorporating a Volterra equalizer with BER of 6.5 x10(-5). Record high bit-rate distance product of 128 Gbps.km is confirmed for optical-interconnect applications.
High-Speed and Duo-Mode 850 nm VCSELs for 47 Gbps Optical Interconnect over 1 km OM4 Fiber
(2015)
Lu, I-Cheng
;
Wei, Chia-Chien
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Chen, Hsing-Yu
;
Chen, Kuan-Zhou
;
Huang, Cheng-Hsiang
Novel duo-mode 850nm VCSELs with short (lambda/2) cavity, oxide-relief and Zn-diffusion apertures are demonstrated to balance the trade-off of speed and reaching bottleneck of VCSELs. Extremely-high data rate (47-Gbps) over 1005m OM4-fiber transmission is reported.
Nonlinear Compensation for 980 nm High Power, Single-Mode VCSELs for Energy Efficient OM 4 Fiber Transmission
(2014-01-01)
Lu, I-Cheng
;
Wei, Chia-Chien
;
Chen, Hsing-Yu
;
Chung, Pei-Yu
;
Huang, Peng-Hao
A nonlinear compensation method is demonstrated to boost the launch power for optical interconnects employing OFDM format. A 1.5 dB sensitivity improvement is obtained for a 2-km OM4 fiber transmission system at 15 Gbit/sec.
Nonlinear Compensation of 850 nm VCSEL with Discrete Multi-Tone Modulation Employing a Volterra-Wiener Filter
(2016)
Tzu, Ta-Ching
;
Wei, Chia-Chien
;
Liu, Jun-Jie
;
Chang, Chun-Yen
;
Chi, Kai-Lun
A DMT transmission with 32% and 21.2% data rate improvement by nonlinear Volterra-Wiener compensation respectively for 68.94Gb/s OBTB and 58.39Gb/s over 105m is demonstrated by a 850nm VCSEL with short (lambda/2) cavity and mode controlled.
Single-Mode 850-nm VCSELs for 54-Gb/s ON-OFF Keying Transmission Over 1-km Multi-Mode Fiber
(2016-06-15)
Chi, Kai-Lun
;
Shi, Yi-Xuan
;
Chen, Xin-Nan
;
Chen, Jason (Jyehong)
;
Yang, Ying-Jay
By combing Zn-diffusion and oxide-relief apertures with strong detuning (>20 nm) in our demonstrated short-cavity (lambda/2) 850-nm vertical-cavity surface-emitting lasers (VCSELs), wide electrical-to-optical bandwidth (29-24 GHz), low-differential resistance (similar to 100 Omega), and (quasi) single-mode (SM) with reasonable output power (similar to 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 (1x10(-5) versus 1x10(-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 similar to 3.5x10(-3) versus similar to 1.4x10(-4) under the same received optical power.
Single-Mode, High-Speed, and High-Power Vertical-Cavity Surface-Emitting Lasers at 850 nm for Short to Medium Reach (2 km) Optical Interconnects
(2013-12-15)
Shi, Jin-Wei
;
Wei, Zhi-Rui
;
Chi, Kai-Lun
;
Jiang, Jia-Wei
;
Wun, Jhih-Min
The vertical-cavity surface-emitting lasers (VCSELs) with high single-mode (narrow linewidth) output power are essential to minimize chromatic dispersion and to further improve the bit-rate distance product in a multimode fiber, which has a significant propagation loss (similar to 3.5 dB/km) at 850 nm wavelength. Here, we demonstrate the detailed design considerations and fabrication of a single-mode, high-power, and high-speed VCSELs at the 850 nm wavelength with oxide-relief and Zn-diffusion apertures for the application of short (0.3 km) to medium reach (2 km) optical interconnects. By optimizing the relative geometric sizes between two such apertures in our demonstrated 850-nm VCSELs, we can not only attain high single-mode output power (similar to 6.5 mW), but also with a reasonable threshold current (< 2.0 mA). Furthermore, the spatial hole burning effect induced low-frequency roll off can also be minimized in our optimized structure to obtain a maximum data rate up to 26 Gbit/s. The record-high bit rate-distance products for OM4 MMF transmission under ON-OFF keying (14 Gbit/s x 2.0 km) modulation formats have been successfully demonstrated by the use of our VCSEL.
Strong Enhancements in Output Power and High-Speed Data Transmission Performances by Using Parallel Oxide-Relief/Zn-Diffusion 850 nm VCSELs
(2016)
Chi, Kai-Lun
;
Chen, Xin-Nan
;
Chen, Jye-Hong
;
Bowers, J. E.
;
Yang, Ying-Jay
By using parallel two high-speed VCSELs, double increase in maximum output power (4 vs. 8mW), negligible degradation in 3-dB electrical-to-optical bandwidth (similar to 25 GHz), and strong enhancement in 46 Gbit/sec data transmission through OM4 MMF is achieved compared with those of single reference.
Strong Enhancements in Static/Dynamic Performances of High-Speed 850 nm Vertical-Cavity Surface-Emitting Lasers with P-type delta-Doping in Highly Strained Active Layers
(2016)
Chi, Kai-Lun
;
Chen, Xin-Nan
;
Yen, Jia-Liang
;
Lin, Wei
;
Chiu, Shi-Wei
By using p-type modulation doping in the highly strained MQWs of high-speed 850 nm VCSELs, significant enhancements in speed, slope efficiency, and maximum power have been simultaneously achieved as compared to those of un-doped references
Strong Wavelength Detuning of 850 nm Vertical-Cavity Surface-Emitting Lasers for High-Speed (>40 Gbit/s) and Low-Energy Consumption Operation
(2015-11-01)
Chi, Kai-Lun
;
Yen, Jia-Liang
;
Wun, Jhih-Min
;
Jiang, Jia-Wei
;
Lu, I-Cheng
The strong (>20 nm) wavelength detuning technique has been demonstrated to enhance the modulation speed and high-temperature characteristics (at 85 degrees C), as well as lower the required driving current density performance of oxide-relief 850-nm vertical-cavity surface-emitting lasers (VCSELs) for >40 Gbit/s operation. By increasing the wavelength detuning from 15 to 20 nm, a significant improvement in the electrical-to-optical (E-O) bandwidth (20 to 27 GHz) of the VCSEL can be observed. This detuning design (similar to 20 nm) is incorporated along with a Zn-diffusion structure into our oxide-relief VCSEL with a miniaturized oxide-relief aperture (similar to 3 mu m). Highly single-mode, high-speed (26 GHz) operation, and moderate differential resistance (100 Omega) values can be simultaneously achieved. In addition, it is found that devices with a further larger detuning wavelength (>20 nm) and enlarged oxide-relief apertures (similar to 8 mu m) can sustain the same maximum E-O bandwidth (26 GHz) as that of a miniaturized (similar to 3 mu m) VCSEL, resulting in the lower driving current density (8 versus 18.8 kA/cm(2)) required for high-speed performance. Excellent transmission performance, which includes an extremely low energy-to-data rate ratio (EDR: 228 fJ/bit; over 100 m OM4 fiber) and record-low driving-current density (8 kA/cm(2); 3.5 mA) has been successfully achieved for 41 Gbit/s error-free transmission for these VCSELs.
Very High Bit-Rate Distance Product Using High-Power Single-Mode 850-nm VCSEL With Discrete Multitone Modulation Formats Through OM4 Multimode Fiber
(2015-11-01)
Lu, I-Cheng
;
Wei, Chia-Chien
;
Chen, Hsing-Yu
;
Chen, Kuan-Zhou
;
Huang, Cheng-Hsiang
In order to investigate the tradeoff between optical spectral width and modulation speed of 850-nm Zn-diffusion vertical-cavity surface-emitting laser (VCSEL) and its influence on the performance of discrete multitone (DMT) modulation, two kinds of high-speed VCSEL structures with different cavity lengths (lambda/2 and 3 lambda/2) are studied. By shortening the cavity length to lambda/2, allocating the oxide layer in the standing-wave peak, and performing a Zn-diffusion aperture in our VCSEL structure, stable dual mode in the output optical spectra across the full range of bias currents with good high-speed performance (similar to 16-GHz bandwidth) can be achieved. Compared with its multimode reference, it shows far less roll-off with regard to the maximum data rate versus transmission distance over OM4 multimode fibers under forward error correction (FEC) threshold (BER < 3.8 x 10(-3)). On the other hand, for the 3 lambda/2 VCSEL structure, by using the same Zn-diffusion conditions as those of dual-mode counterpart, highly single-mode operation (side-mode suppression ratio > 35 dB) with high available power can be achieved over the full range of bias currents. Although such device shows a smaller 3-dB electrical-to-optical bandwidth (12 versus 16 GHz) than that of the dual-mode one, it exhibits a superior transmission performance by use of DMT modulation format. A record high bit-rate distance product (107.6 Gb/s.km) at nearly 50-Gb/s transmission under FEC threshold (BER < 3.8 x 10(-3)) through 2.2-km OM4 fibers has been successfully demonstrated by the use of single-mode VCSEL with optimized structures. In addition, error-free (BER< 1 x 10(-12)) transmission at 20.3 Gb/s with bit-rate distance product of 44.66 Gb/s.km has also been demonstrated.