Degradation Prediction of Semiconductor Lasers using Conditional Variational Autoencoder

Semiconductor lasers have been rapidly evolving to meet the demands of next-generation optical networks. This imposes much more stringent requirements on the laser reliability, which are dominated by degradation mechanisms (e.g., sudden degradation) limiting the semiconductor laser lifetime. Physics-based approaches are often used to characterize the degradation behavior analytically, yet explicit domain knowledge and accurate mathematical models are required. Building such models can be very challenging due to a lack of a full understanding of the complex physical processes inducing the degradation under various operating conditions. To overcome the aforementioned limitations, we propose a new data-driven approach, extracting useful insights from the operational monitored data to predict the degradation trend without requiring any specific knowledge or using any physical model. The proposed approach is based on an unsupervised technique, a conditional variational autoencoder, and validated using vertical-cavity surface-emitting laser (VCSEL) and tunable edge emitting laser reliability data. The experimental results confirm that our model (i) achieves a good degradation prediction and generalization performance by yielding an F1 score of 95.3%, (ii) outperforms several baseline ML based anomaly detection techniques, and (iii) helps to shorten the aging tests by early predicting the failed devices before the end of the test and thereby saving costsComment: Published in: Journal of Lightwave Technology (Volume: 40, Issue: 18, 15 September 2022

Beyond 25 Gb/s Directly-Modulated Widely Tunable VCSEL for Next Generation Access Network

We demonstrate capacities beyond 25Gb/s up to 40 km in the whole C-band range without any dispersion compensation by DMT direct modulation and direct detection exploiting widely tuneable MEMS-VCSELs for future low-cost high-capacity access networks

Optical transmitter based on a 1.3-mu m VCSEL and a SiGe driver circuit for short-reach applications and beyond

Long-wavelength vertical-cavity surface-emitting lasers (LW-VCSELs) with emission wavelength in the 1.3-mu m region for intensity modulation (IM)/direct detection optical transmissions enable longer fiber reach compared to C-band VCSELs, thanks to the extremely low chromatic dispersion impact at that wavelength. A lot of effort has been recently dedicated to novel cavity designs in order to enhance LW-VCSELs' modulation bandwidth to allow higher data rates. Another approach to further improve VCSEL-based IM speed consists of making use of dedicated driver circuits implementing feedforward equalization (FFE). In this paper, we present a transmitter assembly incorporating a four-channel 0.13-mu m SiGe driver circuit wire-bonded to a novel dual 1.3-mu m VCSEL array. The short-cavity indium phosphide buried tunnel junction VCSEL design minimizes both the photon lifetime and the device parasitic currents. The integrated driver circuit requires 2.5-V supply voltage only due to the implementation of a pseudobalanced regulator; it includes a two-tap asymmetric FFE, where magnitude, sign, relative delay, and pulse width distortion of the taps can be modified. Through the proposed transmitter, standard single-mode fiber reach of 20 and 4.5 km, respectively, for 28- and 40-Gb/s data rate has been demonstrated with state-of-the-art power consumption. Transmitter performance has been analyzed through pseudorandom bit sequences of both 2(7)-1 and 2(31)-1 length, and the additional benefit due to the use of the driver circuit has been discussed in detail. A final comparison with state-of-the-art VCSEL drivers is also includedt

Malignant peripheral nerve sheath tumor of the mediastinum: A temporary aortic transection approach

Unprecedented standard single-mode fiber reach of 20km and 4.5km respectively for 28Gb/s and 40Gb/s VCSEL-based intensity-modulation/direct detection optical transmission was obtained with a low-power transmitter assembly including a 4-channel 0.13-μm SiGe driver wire-bonded to a novel 2×1 1.3pm-VCSEL array

All-VCSEL based digital coherent detection link for multi Gbit/s WDM passive optical networks

We report on experimental demonstration of a digital coherent detection link fully based on vertical cavity surface emitting lasers (VCSELs) for the transmitter as well as for the local oscillator light source at the receiver side. We demonstrate operation at 5 Gbps at a 1550 nm wavelength with record receiver sensitivity of -36 dBm after transmission over 40 km standard single mode fiber. Digital signal processing compensates for frequency offset between the transmitter and the local oscillator VCSELs, and for chromatic dispersion. This system allows for uncooled VCSEL operation and fully passive fiber transmission with no use of optical amplification or optical dispersion compensation. The proposed system demonstrates the potential of multi-gigabit coherent passive optical networks with extended reach and increased capacity. Moreover, this is, to the best of our knowledge, the first demonstration of coherent optical transmission systems using a low-cost VCSEL as the local oscillator as well as for the transmitter

Free-Running 1550 nm VCSEL for 10.7 Gb/s Transmission in 99.7 km PON

We present a cooler-less, free-running 1550 nm vertical cavity surface emitting laser (VCSEL) directly modulated at 10.7 Gb/s. We also report on error-free transmission through 40 km of standard single-mode optical fiber, achieved without the use of dispersion-mitigation or mid-span amplification. Inverse-dispersion fiber was utilized to realize a dispersion-matched 99.7 km optical access uplink supporting error-free transmission with 27 dB loss margin. These results indicate the feasibility of implementing cooler-less long-wavelength VCSEL devices in long-reach optical access networks

Geological Reconnaissance along the Alaska Highway from Fort Nelson, British Columbia, to Watson Lake, Yukon:

by M. Y. Williams.Paper (Geological Survey of Canada) ; 44-28

Impact of Chirp in High-Capacity Optical Metro Networks Employing Directly-Modulated VCSELs

Directly modulated long-wavelength vertical cavity surface emitting lasers (VCSELs) are considered for the implementation of sliceable bandwidth/bitrate variable transceivers for very high capacity transmission (higher than 50 Gb/s per wavelength) in metropolitan area systems characterized by reduced cost, power consumption, and footprint. The impact of the frequency chirp measured for InP VCSELs with different kinds of design (high-bandwidth very short cavity and widely-tunable with micro electro-mechanical systems (MEMS) top mirror) is analyzed in case of discrete multitone (DMT) direct modulation in combination with 25-GHz wavelength selective switch (WSS) filtering. The maximum transmitted capacity for both dual side- and single side-band DMT modulation is evaluated as a function of the number of crossed nodes in a mesh metro network, comparing VCSEL based transmitters performance also with the case of external electro-absorption modulator use. Finally, the maximum reach achieved based on the received optical signal to noise ratio (OSNR) and the fiber span length is discussed. The results confirm the possibility to use directly-modulated long-wavelength VCSELs for the realization of sliceable bandwidth/bitrate variable transmitters targeting 50-Gb/s capacity per polarization, also in the presence of 5 crossed WSSs for reaches of hundreds of kilometers in multi-span Erbium-doped fiber amplified (EDFA) metro links supported by coherent detection