| 1. |
- Bamiedakis, N., et al.
(författare)
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40 Gb/s Data Transmission Over a 1-m-Long Multimode Polymer Spiral Waveguide for Board-Level Optical Interconnects
- 2015
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 33:4, s. 882-888
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Tidskriftsartikel (refereegranskat)abstract
- Optical interconnects have attracted considerable attention for use in short-reach communication links within high-performance electronic systems, such as data centers, supercomputers, and data storage systems. Multimode polymer waveguides, in particular, constitute an attractive technology for use in board-level interconnects as they can be cost-effectively integrated onto standard PCBs and allow system assembly with relaxed alignment tolerances. However, their highly multimoded nature raises important concerns about their bandwidth limitations and their potential to support very high on-board data rates. In this paper, we report record error-free (BER
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| 2. |
- Carlsson, Christina, 1975, et al.
(författare)
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RF transmission over multimode fibers using VCSELs-comparing standard and high bandwidth multimode fibers
- 2004
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 22:7, s. 1694-1700
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Tidskriftsartikel (refereegranskat)abstract
- Fiber-optic radio-frequency links have been assembled using oxide-confined vertical-cavity surface-emitting lasers (VCSELs) and multimode fibers. Links with single and multimode VCSELs and with standard and high-bandwidth fibers have been evaluated and compared in the frequency range of 0.1-10 GHz. The best results were obtained for links with a multimode VCSEL and a high-bandwidth fiber. For a 500-m-long link, a spurious free dynamic range of 104 dB. HZ(2/3) at 2 GHz and 100 dB (.) Hz(2/3) at 5, GHz were obtained while allowing for a VCSEL-fiber misalignment of +/-12 mum. Corresponding numbers for the intrinsic link gain and noise figure are -29 and -33 dB, and 39 and 42 dB at 2 and 5 GHz, respectively. Inferior performance Was observed for the standard fiber link due to a larger variation in modal group velocities. This paper also presents a detailed link analysis to identify performance limitations and to suggest modifications for improved performance.
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| 3. |
- Castro, J. M., et al.
(författare)
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Investigation of 60 Gb/s 4-PAM Using an 850 nm VCSEL and Multimode Fiber
- 2016
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 34:16, s. 3825-3836
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Tidskriftsartikel (refereegranskat)abstract
- We investigate 4-pulse-amplitude modulation (PAM) at data rates in the range of 50-60 Gb/s using a directly modulated 850 nm VCSEL and multimode fiber links up to 200 m. The channel conditions in which 4-PAM has performance advantages over traditional ON-OFF keying are evaluated followed by experimental results at data rates of 56.7 Gb/s over distances up to 200 m using equalization and FEC, with a post-FEC bit error rate of 10(-12). The reported analysis is applicable to future Ethernet and Fibre Channel applications requiring 50 Gb/s serial data rates per lane over multimode fibers.
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| 4. |
- Caut, Alexander, 1994, et al.
(författare)
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Angled Flip-Chip Integration of VCSELs on Silicon Photonic Integrated Circuits
- 2022
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 40:15, s. 5190-5200
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Tidskriftsartikel (refereegranskat)abstract
- An investigation of angled flip-chip integration of a singlemode 850 nm vertical-cavity surface-emitting laser (VCSEL) on a silicon nitride photonic integrated circuit (PIC) is presented. Using numerical FDTD simulations, we consider the conditions under which the VCSEL can be integrated at an angle over a grating coupler with high coupling efficiency and low optical feedback. With both coupling efficiency and feedback decreasing with increasing angle, there is a trade-off. With co-directional coupling, first-order diffraction loss sets in at a critical angle, which further reduces the coupling efficiency. No such critical angle exists for contra-directional coupling. We also experimentally demonstrate angled flip-chip integration of GaAs-based 850 nm single transverse and polarization mode VCSELs over grating couplers on a silicon-nitride PIC. At the output grating coupler, light is either collected by an optical fiber or converted to a photocurrent using a flip-chip integrated GaAs-based photodetector. The latter forms an on-PIC optical link. We measured an insertion loss of 21.9, 17.6 and 20.1 dB with a singlemode fiber, multimode fiber and photodetector over the output grating coupler, respectively.
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| 5. |
- Caut, Alexander, 1994, et al.
(författare)
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Channel Scalability of Silicon Nitride (De-)multiplexers for Optical Interconnects at 1 μm
- 2024
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 42:1, s. 276-286
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an investigation of the channel scalability of silicon nitride (Si3N4)-based (de-)multiplexers in the 1-μm band (1015-1055 nm). We discuss 4-, 8- and 16-channel demultiplexers based on arrayed waveguide gratings (AWGs) and cascaded Mach-Zehnder interferometers (MZIs), with corresponding channel spacings of 8, 4 and 2 nm. Gaussian and flat-top response devices are considered for both technologies and we analyze the insertion loss, temperature sensitivity, response flatness, footprint and crosstalk (XT). We study the impact of the number of channels on the insertion loss and XT level. In the experimental part, we demonstrate a 4-channel Gaussian AWG. We also demonstrate 4-channel Gaussian and flat-top cascaded MZIs, based on multimode interferometers (MMIs) and directional couplers (DCs). The AWG is attractive due to its small footprint but its high manufacturing complexity makes the device more prone to fabrication defects, which can lead to higher loss and higher XT. For the Gaussian AWG and MZI, the XT level is approximately the same and increases with the number of channels from -28 to -23 dB at 4 and 16 channels respectively. The flat-top MZI has no extra-loss with respect to the flat-top AWG and has a better tolerance to high temperature operations. However, due to wavelength sensitive DCs, the XT of the flat-top MZI is higher than that of the flat-top AWG except for a 16-channel system.
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| 6. |
- Chen, Jingjing, 1982, et al.
(författare)
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An Energy Efficient 56 Gbps PAM-4 VCSEL Transmitter Enabled by a 100 Gbps Driver in 0.25 µm InP DHBT Technology
- 2016
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 34:21, s. 954-4964
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Tidskriftsartikel (refereegranskat)abstract
- Datacenters demand higher speed VCSEL-based optical interconnects at low power consumption. As a potential technology enabler, this paper presents a wide bandwidth and energy efficient multilevel PAM VCSEL driver implemented in an InP 0.25 μm double heterojunction bipolar transistor (DHBT) technology. The operational bandwidth of the driver is verified and error-free electrical data transmission up to 56 Gbps PAM-2 and 100 Gbps PAM-4 is demonstrated at a driver energy consumption less than 2 pJ/bit. The driver is integrated and tested with an in-house fabricated 850 nm VCSEL. Error-free 56 Gbps PAM-4 optical transmission at a transmitter energy consumption of 3.7 pJ/bit is demonstrated without equalization. This is the highest data rate reported for an integrated PAM-4 modulated VCSEL transmitter, while being the most energy efficient above 40 Gbps operation. Moreover, the VCSEL driver offers a pre-emphasis feature at PAM-2 operation for improved link throughput and receiver sensitivity.
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| 7. |
- Grabowski, Alexander, 1993, et al.
(författare)
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Large-Signal Equivalent Circuit for Datacom VCSELs
- 2021
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 39:10, s. 3225-3236
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Tidskriftsartikel (refereegranskat)abstract
- Increasing the baud rate in optical interconnects (OIs) will require the use of more sophisticated driver and receiver electronics. This will help overcome the stagnated bandwidth of the Vertical-Cavity Surface-Emitting Laser (VCSEL) and the pin-photodetector. Next generation OIs operating at single lane rates of 50+ Gbaud will therefore require careful co-optimization of the electronics and the optoelectronics. To facilitate this work there is a need of an accurate equivalent circuit for the optoelectronic components, functioning over a broad drive current and ambient temperature range. The VCSEL is the most important and complex to model due to its non-linear behavior and strongly varying characteristics with drive current and ambient temperature. For this purpose, a large-signal equivalent circuit dedicated for high-speed datacom VCSELs has been developed and is presented here. The distributed electrical parasitics in the device layout are carefully considered, the intrinsic speed limitation from carrier transport effects in the Separate-Confinement-Heterostructure (SCH) and the carrier-photon interaction in the Quantum Wells (QWs) are included, and self-heating effects in the device are monitored. The circuit is purposely based on physical instead of empirical models so that it can provide usable feedback to VCSEL designers. For circuit demonstration, it is implemented in Keysight's Advanced Design System (ADS) software and thereafter applied to replicate the performance of a state-of-the-art 28-GHz-bandwidth VCSEL at different temperatures and drive currents. Comparison is made between simulated and measured steady-state characteristics, small-signal behavior, and large-signal response under 28 Gbaud On-Off-Keying (OOK) and Pulse-Amplitude-Modulation 4 (PAM4) modulation, showing good agreement.
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| 8. |
- Grabowski, Alexander, 1993, et al.
(författare)
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Large-Signal Equivalent Circuit for Datacom VCSELs – Including Intensity Noise
- 2022
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 40, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Optical interconnects (OIs) continue to require more and more sophisticated driver and receiver electronics as higher baud rates are pushed in datacom, mainly due to the bandwidth stagnation of the optoelectronic components such as the vertical-cavity surface-emitting laser (VCSEL) in the transmitter as well as the photodetector (PD) in the receiver. Another important focus is maintaining high energy efficiency for the OIs. For both cases, a reliable equivalent circuit model for high-speed VCSELs is required for link optimization. This work is an extension of our previously presented large-signal VCSEL equivalent circuit model, where noise is added to the physical processes that the VCSEL model is based on. Thus, a new step is taken in the strive of developing an even more accurate physics-based large-signal VCSEL equivalent circuit model for datacom applications. Following a detailed description of the VCSEL noise modelling, a presentation is given on simulated results of VCSEL relative intensity noise (RIN) spectrum and eye diagrams under 28 Gbaud on-off keying (OOK) and pulse-amplitude 4 (PAM4) modulation, and that are compared with corresponding measurement results. Good agreement is found over a wide range of VCSEL driving conditions and temperatures. A 28-GHz-bandwidth VCSEL is applied for the demonstration, and the presented noise extended VCSEL equivalent circuit model was implemented in Verilog-A, and the simulations were performed using Cadence Spectre.
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| 9. |
- Haglund, Erik, 1985, et al.
(författare)
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High-Speed VCSELs with Strong Confinement of Optical Fields and Carriers
- 2016
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 34:2, s. 269-277
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Tidskriftsartikel (refereegranskat)abstract
- We present the design, fabrication, and performance of our latest generation high-speed oxide-confined 850-nm verticalcavity surface-emitting lasers. Excellent high-speed properties are obtained by strong confinement of optical fields and carriers. Highspeed modulation is facilitated by using the shortest possible cavity length of one half wavelength and placing oxide apertures close to the active region to efficiently confine charge carriers. The resulting strong current confinement boosts internal quantum efficiency, leading to low threshold currents, high wall-plug efficiency, and state-of-the-art high-speed properties at low bias currents. The temperature dependent static and dynamic performance is analyzed by current-power-voltage and small-signal modulation measurements.
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| 10. |
- Haglund, Emanuel, 1988, et al.
(författare)
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Impact of Damping on High-Speed Large Signal VCSEL Dynamics
- 2015
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 33:4, s. 795 - 801
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Tidskriftsartikel (refereegranskat)abstract
- An investigation of the optimal relaxation oscillation damping for high-speed 850-nm vertical-cavity surface-emitting laser (VCSEL) under large signal operation is presented, using devices with K-factors ranging from 0.1 to 0.4 ns. Time-domain measurements of turn-on transients are used to quantify damping dependent rise times, overshoots, and signal amplitudes. Optical eye diagrams together with timing jitter and bit error rate measurements reveal a tradeoff between the rise time and the duration of the relaxation oscillations. To produce a high-quality eye at a specific data rate, a proper amount of damping is needed to simultaneously obtain sufficiently high bandwidth and low timing jitter. We found that for error-free transmission, a VCSEL with a 0.3 ns K-factor achieved the best receiver sensitivity at 10 and 25 Gb/s, whereas a less damped VCSEL with a 0.2 ns K-factor achieved the best sensitivity at 40 Gb/s.
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