| 241. |
- Larsson, Rasmus, 1994, et al.
(författare)
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Coherent combining of low-power optical signals based on optically amplified error feedback
- 2022
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 30:11, s. 19441-19455
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Tidskriftsartikel (refereegranskat)abstract
- In free-space optical communication links, the combining of optical signals from multiple apertures is a well-known method to collect more power for improved sensitivity or mitigation of atmospheric disturbances. However, for analog optical combining no detailed analysis has been made in cases when the optical signal power is very low (<-60 dBm) as would be the case in very long-haul free-space links. We present a theoretical and experimental study of analog coherent combining of noise-limited signals from multiple independent apertures by applying low frequency optical phase dithering to actively compensate the relative phases. It is experimentally demonstrated that a 97% combining efficiency of four 10 GBaud QPSK signals is possible with a signal power per aperture exceeding -80 dBm, in fair agreement with theory. We also discuss the scaling aspects to many apertures.
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| 242. |
- Lei, Fuchuan, 1987, et al.
(författare)
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Self-injection-locked optical parametric oscillator based on microcombs
- 2024
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Ingår i: Optica. - 2334-2536. ; 11:3, s. 420-426
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Tidskriftsartikel (refereegranskat)abstract
- Narrow-linewidth yet tunable laser oscillators are one of the most important tools for precision metrology, optical atomic clocks, sensing, and quantum computing. Commonly used tunable coherent oscillators are based on stimulated emission or stimulated Brillouin scattering; as a result, the operating wavelength band is limited by the gain media. Based on nonlinear optical gain, optical parametric oscillators (OPOs) enable coherent signal generation within the whole transparency window of the medium used. However, the demonstration of OPO-basedHertz-level linewidth and tunable oscillators has remained elusive. Here, we present a tunable coherent oscillator based on a multimode coherent OPO in a high-Q microresonator, i.e., a microcomb. Single-mode coherent oscillation is realized through self-injection locking (SIL) of one selected comb line. We achieve coarse tuning up to 20 nm and an intrinsic linewidth down to sub- Hertz level, which is three orders of magnitude lower than the pump. Furthermore, we demonstrate that this scheme results in the repetition rate stabilization of the microcomb. These results open exciting possibilities for generating tunable coherent radiation where stimulated emission materials are difficult to obtain, and the stabilization of microcomb sources beyond the limits imposed by the thermorefractive noise in the cavity.
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| 243. |
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| 244. |
- Lengyel, Tamas, 1986, et al.
(författare)
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Impact of Damping on 50 Gbps 4-PAM Modulation of 25G Class VCSELs
- 2017
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Ingår i: Optics InfoBase Conference Papers. - 2162-2701. - 9781943580231 ; , s. paper W3G.2-
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Konferensbidrag (refereegranskat)abstract
- We investigate the effects of photon lifetime and damping of the modulation response on the quality of 50 Gbps 4-PAM signal generation with directly modulated 25G class VCSELs and identify the appropriate values for the K-factor.
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| 245. |
- Lengyel, Tamas, 1986, et al.
(författare)
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Impact of Damping on 50 Gbps 4-PAM Modulation of 25G Class VCSELs
- 2017
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 35:19, s. 4203-4209
-
Tidskriftsartikel (refereegranskat)abstract
- We present an investigation into the effects of photon lifetime and the associated damping of the modulation response on 50 Gbps 4-PAM signal generation with directly modulated 25G class VCSELs. While 4-PAM benefits from higher slope efficiency and output power, it is shown that the greater impact of intensity noise and dynamic nonlinearities implies that a VCSEL with a longer photon lifetime and more damped response is needed when transitioning from existing 25 Gbps OOK to 50 Gbps 4-PAM using the 25G VCSEL technology.
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| 246. |
- Lengyel, Tamas, 1986, et al.
(författare)
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Pre-emphasis enabled 50 Gbit/s transmission over 1000 m SMF using a 1060 nm single-mode VCSEL
- 2018
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 54:20, s. 1186-1187
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Tidskriftsartikel (refereegranskat)abstract
- A single-mode 1060 nm vertical-cavity surface-emitting laser (VCSEL) and single-mode fibre (SMF) based link with two-tap active pre-emphasis enabling error-free transmission of 50 Gbit/s NRZ-OOK over 1000 m is presented.
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| 247. |
- Lengyel, Tamas, 1986, et al.
(författare)
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Sensitivity Improvements in an 850 nm VCSEL-based Link using a Two-tap Pre-emphasis Electronic Filter
- 2016
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 35:9, s. 1633-1639
-
Tidskriftsartikel (refereegranskat)abstract
- We present an investigation of an ISI penalty reduction for On-Off Keying in an 850 nm VCSEL-based short optical link using a two-tap electronic pre-emphasis filter and quantify the improvement relative to an equivalent link without pre-emphasis. Error-free operation is demonstrated at bit rates above the −3 dB modulation bandwidth of the link. Sensitivity improvement up to 9 dB compared to non-emphasized signaling is shown. A maximum error-free bit rate achievable in the link is increased to 57 Gbps, compared to 52 Gbps without the pre-emphasis.
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| 248. |
- Lengyel, Tamas, 1986, et al.
(författare)
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Sensitivity improvements in an 850 nm VCSEL transmitter using a one-tap pre-emphasis electronic filter
- 2015
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Ingår i: 41st European Conference on Optical Communication, ECOC 2015, Valencia, Spain, 27 September - 1 October 2015. - 9788460817413 ; 2015-November
-
Konferensbidrag (refereegranskat)abstract
- We present ISI reduction of an 850 nm VCSEL-based back-to-back optical link using a one-tap electronic pre-emphasis filter and compare it to a VCSEL link without filtering with similar launch conditions. Error floors are eliminated by the use of the filter.
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| 249. |
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| 250. |
- Li, Jie, 1967, et al.
(författare)
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0.5 Tbit/s eye-diagram measurement by optical sampling using XPM-induced wavelength shifting in highly nonlinear fiber
- 2003
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Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 16:2, s. 566-568
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, we report on a novel all-optical sampling scheme using cross-phase modulation-induced wavelength shifting and optical filtering. Up to 500-Gb/s optical signal eye-diagram measurements have been demonstrated for the first time with a temporal resolution of 0.7 ps. Signal operational wavelength range covering basically the whole erbium-doped fiber amplifier gain range (1535-1569 nm) with temporal resolutions equal to or less than 1 ps was also demonstrated in the experiment. These results show that the sampling system is suitable for directly monitoring and evaluating ultrahigh bit-rate optical time-division multiplexed data at or above 160 Gb/s.
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