| 1. |
- Bengtsson, Magnus, et al.
(author)
-
Fluorescence lidar imaging of fungal growth on high-voltage outdoor composite insulators
- 2005
-
In: Optics and Lasers in Engineering. - : Elsevier BV. - 0143-8166 .- 1873-0302. ; 43:6, s. 624-632
-
Journal article (peer-reviewed)abstract
- Remote fluorescence imaging of fungal growth on polymeric high-voltage insulators was performed using a mobile lidar system with a laser wavelength of 355 nm. Insulator areas contaminated by fungal growth could be distinguished from clean surfaces and readily be imaged. The experiments were supported by detailed spectral studies performed in laboratory using a fibre-optic fluorosensor incorporating an optical multi-channel analyser system (OMA) and a nitrogen laser emitting radiation at 33 7 nm.
|
|
| 2. |
- Lavrencik, Justin, et al.
(author)
-
Error-Free 100Gbps PAM-4 Transmission over 100m Wideband Fiber using 850nm VCSELs
- 2017
-
In: European Conference on Optical Communication, ECOC. ; 2017-September, s. 1-3
-
Conference paper (peer-reviewed)abstract
- We experimentally demonstrate error-free rates beyond 100Gbps over 100m WBMMF. Power penalties and maximum data rates of PAM-2 and PAM-4 using shaped and unshaped pulses were studied. The link includes unpackaged 850nm VCSELs with different apertures and only transmitter equalization.
|
|
| 3. |
- Grabowski, Alexander, 1993, et al.
(author)
-
Impact of Carrier Transport and Capture on VCSEL Dynamics
- 2023
-
In: IEEE Journal of Quantum Electronics. - 0018-9197 .- 1558-1713. ; 59:1, s. 1-6
-
Journal article (peer-reviewed)abstract
- Using a vertical-cavity surface-emitting laser (VCSEL) equivalent circuit model based on two carrier rate equations to include effects of carrier dynamics, we study the impact of carrier transport and capture on the small- and large-signal modulation response of high-speed VCSELs. The model also accounts for parasitics, current-induced self-heating, and gain compression. A variation of the effective capture time from 1 to 15 ps is found to have a large impact on the small-signal modulation response, with the 3 dB bandwidth decreasing from 40 to 15 GHz and the response transitioning from under-damped to over-damped. This is primarily due to the increasing low frequency parasitic-like roll-off with increasing effective capture time. A significant effect on the optical waveforms produced by the VCSEL under 56 Gbit/s on-off keying (OOK) non-return-to-zero (NRZ) and pulse-amplitude modulation 4 (PAM4) modulation is observed, with a short effective capture time leading to horizontal eye closure caused by timing jitter (TJ) and intersymbol interference (ISI) and a long effective capture time leading to vertical eye closure caused by long rise- and fall-times. However, for high modulation speed, a short effective capture time is needed and the photon lifetime should be set for clear eye opening. We also show the impact of the effective capture time on the output power vs current characteristics and map the dependence of internal temperature, carrier densities, carrier escape and leakage rates, and spontaneous recombination rates on current for different effective capture times.
|
|
| 4. |
- Srinivasan, Muralikrishnan, 1991, et al.
(author)
-
End-to-End Learning for VCSEL-based Optical Interconnects: State-of-the-Art, Challenges, and Opportunities
- 2023
-
In: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 41:11, s. 3261-3277
-
Journal article (peer-reviewed)abstract
- Optical interconnects (OIs) based on vertical-cavity surface-emitting lasers (VCSELs) are the main workhorse within data centers, supercomputers, and even vehicles, providing low-cost, high-rate connectivity. VCSELs must operate under extremely harsh and time-varying conditions, thus requiring adaptive and flexible designs of the communication chain. Such designs can be built based on mathematical models (model-based design) or learned from data (machine learning (ML) based design). Various ML techniques have recently come to the forefront, replacing individual components in the transmitters and receivers with deep neural networks. Beyond such component-wise learning, end-to-end (E2E) autoencoder approaches can reach the ultimate performance through co-optimizing entire parameterized transmitters and receivers. This tutorial paper aims to provide an overview of ML for VCSEL-based OIs, with a focus on E2E approaches, dealing specifically with the unique challenges facing VCSELs, such as the wide temperature variations and complex models.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Simpanen, Ewa, 1987, et al.
(author)
-
1060 nm VCSEL for up to 40 Gbit/s Data Transmission
- 2016
-
In: Conference Digest - IEEE International Semiconductor Laser Conference. - 0899-9406. - 9784885523069 ; , s. Article no 7765757-
-
Conference paper (peer-reviewed)abstract
- A GaAs-based 1060 nm VCSEL with strained InGaAs/GaAsP QWs, doped DBRs, a short optical cavity, and multiple oxide apertures is presented. Modulation up to 40 Gbit/s at 25°C and 30 Gbit/s at 85°C is demonstrated.
|
|
| 8. |
- Szczerba, Krzysztof, 1985, et al.
(author)
-
70 Gbps 4-PAM and 56 Gbps 8-PAM Using an 850 nm VCSEL
- 2015
-
In: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 33:7, s. 1395-1401
-
Journal article (peer-reviewed)abstract
- We present 56 Gbps unequalized 8-pulse-amplitude-modulation (PAM) real-time transmission over 50 m of multimode fiber and 70 Gbps 4-PAM operation with offline equalization. FEC would be necessary in both schemes. The bit-rates are given taking into account the FEC overhead needed to reach a BER below 10-12. The experiments were performed with an 850 nm vertical cavity surface emitting laser with 20 GHz bandwidth and a 22 GHz photoreceiver. We show that 8-PAM modulation requires channel bandwidth comparable with the symbol rate to avoid excessive ISI penalty and that equalization of 4-PAM signal can significantly improve achievable bit-rates.
|
|
| 9. |
- Szczerba, Krzysztof, 1985, et al.
(author)
-
70 Gbps 4-PAM and 56 Gbps 8-PAM using an 850 nm VCSEL
- 2014
-
In: 2014 European Conference on Optical Communication, ECOC 2014; Cannes; France; 21 September 2014 through 25 September 2014. - 9782954944401 ; , s. Art. no. 6963923-
-
Conference paper (peer-reviewed)abstract
- t We present 56 Gbps unequalized 8-PAM real-time transmission over 50 m of MMF and 70Gbps 4-PAM operation with offline equalization. The experiments were performed with an 850 nm VCSEL with 25 GHz bandwidth and a 22 GHz photoreceiver.
|
|
| 10. |
- Szczerba, Krzysztof, 1985, et al.
(author)
-
Energy Efficiency of VCSELs in the Context of Short-Range Optical Links.
- 2015
-
In: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 27:16, s. 1749-1752
-
Journal article (peer-reviewed)abstract
- We present results from an investigation of theenergy efficiency of VCSELs under large signal modulation. We show that the most important factor influencing the energy consumption of the VCSELs is the required optical modulation amplitude, which drives other VCSEL design requirements. The required optical modulation amplitude also depends on the optical link design. Through this dependence it is possible to better understand the energy consumption of complete short range optical links.
|
|
