Dragan Pikula

Unrepeatered 256 Gb/s PM-16QAM transmission over up to 304 km with simple system configurations

We study unrepeatered transmission of 40x256 Gb/s systems with polarization-multiplexed 16-quadrature amplitude modulation (PM-16QAM) channels using simple coherent optical system configurations. Three systems are investigated with either a homogeneous fiber span, or simple two-segment hybrid fiber designs. Each system relies primarily on ultra-low loss, very large effective area fiber, while making use of only first-order backward pumped Raman amplification and no remote optically pumped amplifier (ROPA). For the longest span studied, we demonstrate unrepeatered 256 Gb/s transmission over 304 km with the additional aid of nonlinear compensation using digital backpropagation. We find an average performance improvement in terms of the Q-factor of 0.45 dB by using digital backpropagation compared to the case of using chromatic dispersion compensation alone for an unrepeatered span system.

Efficient and compact green laser for micro-projector applications

— Efficient and compact green lasers are keystone components for micro-projector applications in mobile devices. An architecture that consists of an infrared-producing DBR (distributed Bragg reflector) laser with a frequency-doubling crystal is used to synthesize a green laser that has high electrical-to-optical conversion efficiency and can be modulated at speeds required for scanner-based projectors. The design and performance of a green-laser package that uses adaptive optics to overcome the challenge of maintaining alignment between the waveguides of the DBR laser and the frequency-doubling crystal over temperature and lifetime is described. The adaptive optics technology that is employed uses the piezo-based smooth impact drive mechanism (SIDM) actuators that offer a very small step size and a range of travel adequate for the alignment operation. The laser is shown to be compact (0.7 cm3 in volume) and capable of a wall-plug efficiency approaching 10% (at 100-mW green power). It was demonstrated that the adaptive optics enables operation over a wide temperature range (10–60°C) and provides the capability for low-cost assembly of the device.

Nonlinearity Compensation of 224 Gb/s Dual-Polarization 16-QAM Transmission Over 2700 km

Long-haul transmission for distances greater than 2000 km is investigated for a 224 Gb/s dual-polarization 16-ary quadrature-amplitude-modulation signal, using ultralarge effective area fiber with span lengths of 75.5 km and distributed Raman amplification. By using nonlinear compensation (NLC) based on the low-pass filter (LPF) assisted digital back propagation (DBP) algorithm, a transmission distance of 2700 km is demonstrated with moderate complexity (0.25 backpropagation steps/span) and good robustness to deviation of the algorithm parameters from their optimum values. Compared to the standard DBP algorithm, the LPF assisted DBP algorithm can allow a reduction in the number of NLC steps/span, but with an increased computational complexity for each step. The two DBP algorithms are compared in terms of the number of real multiplications per bit, thus allowing the algorithm with lower complexity to be determined for a given level of performance.

63.2: Distinguished Paper: Efficient and Compact Green Laser Incorporating Adaptive Optics for Wide Operating Temperature Range

Green lasers with high efficiency are keystone components for mobile projectors. We demonstrate a miniature device (<0.7 cc volume) that utilizes adaptive optics for operation over a 50 °C temperature range without requiring a thermo-electric cooler. The use of adaptive optics also helps in reducing the cost of the laser assembly.

Study of EDFA and Raman system transmission reach with 256 Gb/s PM-16QAM signals over three optical fibers with 100 km spans

We compare the transmission performance of three different optical fibers in separate 256 Gb/s PM-16QAM systems amplified with erbium doped fiber amplifiers (EDFAs) and distributed Raman amplification. The span length in each system is 100 km. The fibers studied include standard single-mode fiber, single-mode fiber with ultra-low loss, and ultra-low loss fiber with large effective area. We find that the single-mode fiber with ultra-low loss and the large effective area fiber with ultra-low loss afford reach advantages of up to about 31% and 80%, respectively, over standard fiber measured at distances with 3 dB margin over the forward error correction (FEC) threshold. The Raman amplified systems provide about 50% reach length enhancement over the EDFA systems for all three fibers in the experimental set-up. For the best performing fiber with large effective area and ultra-low loss, the absolute reach lengths with 3 dB margin are greater than 1140 km and 1700 km for the for EDFA and Raman systems, respectively.

Time-resolved performance analysis of a second-order PMD compensator

Design, test, and performance requirement and analysis for a polarization-mode-dispersion compensator (PMDC) with four degrees of freedom is presented. The performance is analyzed on the basis of time-integrated and time-resolved bit-error ratio (BER) measurements. Signal impairments are generated by both, first- and higher-order emulators. The probability distributions of bit errors measured over many one second intervals exhibit very long tails. Therefore even a PMDC with a good average BER performance may result in a significant total outage time for a given system.

Ultra-long-haul 112 Gb/s PM-QPSK transmission systems using longer spans and Raman amplification

Ultra-long-haul transmission at distances greater than 10,000 km is investigated for 112 Gb/s PM-QPSK signals using span lengths of 75 km and 100 km and all-Raman amplification. Two different ultra-low loss and large effective area optical fibers are studied. We demonstrate a reach length of 10,200 km for a 40 channel system using a fiber with effective area 112 μm(2) with 100 km spans, and a reach length of 13,288 km for a system with 75 km spans using a fiber with effective area of 134 μm(2).

Wavelength tunable high-power single-mode 1060-nm DBR lasers

The wavelength tunable 1060-nm distributed Bragg reflector (DBR) laser chip consists of three sections: a gain section for lasing, and phase and DBR sections for wavelength control. A micro-heater is lithographically integrated on the top of the DBR section to tune the emission wavelength. The phase section is designed with either a top heater or by current injection to provide fine tuning of the wavelength. The wavelength tuning efficiency of our DBR laser is approximately 9 nm/W at the laser heat sink temperature of 25°C. Single-mode output powers of 686 mW and 605 mW were obtained at a CW gain drive current of 1.25 A and heat sink temperatures of 25°C and 60°C, respectively. Gain-switching by applying 1.1 GHz sinusoidal signal mixed with 600 mA DC injection current produced approximately 58 ps long optical pulses with 3.1 W peak power and 228 mW average power. The average power increased to 267 mW and pulse width broadened to 70 ps with DC bias of 700 mA. In CW operation, one of the applications for high-power single-mode DBR lasers is for non-linear frequency conversion. The light emitted from the 1060-nm DBR laser chip was coupled into a single-mode periodically poled lithium niobate (PPLN) crystal waveguide. Up to 350 mW optical power at 530 nm with the wall-plug efficiency of up to 15% was demonstrated.

P-233: Multimode DBR Laser Operation for Frequency Doubled Green Lasers in Projection Displays

In frequency doubled green lasers for laser scanning micro projectors, the wavelength fluctuations can create low spatial frequency and repeatable image artifacts that significantly degrade the image quality. We demonstrate a technique where the laser gain current is repeatedly reset to zero and the laser phase is randomized, both at high frequency. The image defects are replaced by high spatial frequency content noise that minimizes the detrimental effects in the human vision system.

Touch sensing analysis using multi-modal acquisition system

Touch sensing is ubiquitous in many consumer electronic products. Users are expecting to be able to touch with their finger the surface of a display and interact with it. Yet, the actual mechanics and physics of the touch process are little known, as these are dependent on many independent variables. Ranging from the physics of the fingertip structure, composed of ridges, valleys, and pores, and beyond a few layers of skin and flesh the bone itself. Moreover, sweat glands and wetting are critical as well as we will see. As for the mechanics, the pressure at which one touches the screen, and the manner by which the surfaces responds to this pressure, have major impact on the touch sensing. In addition, different touch sensing methods, like capacitive or optical, will have different dependencies. For example, the color of the finger might impact the latter, whereas the former is insensitive to it. In this paper we describe a system that captures multiple modalities of the touch event, and by post-processing synchronizing all these. This enables us to look for correlation between various effects, and uncover their influence on the performance of the touch sensing algorithms. Moreover, investigating these relations allows us to improve various sensing algorithms, as well as find areas where they complement each other. We conclude by pointing to possible future extensions and applications of this system.