Application Of Semiconductor Optical Amplifiers In High-Speed All: Fill & Download for Free

I think the biggest step forward in semiconductors is going to be heterogeneous integration of different kinds of devices and systems on the same substrate or on an interposer. This means that we want to integrate digital logic, analog RF circuits, photonics and optics, micro-electromechanical System (MEMs).As computing retirements get more and more demanding, there are obvious benefits to being able to integrate optical interconnects on a multi-die hip, to act as a communication link between different sub-block. This has very big implications for future computer architectures. Here’s an example: why is cache so precious and such high-speed memory? Because it is physically closest to the CPU. But if we use optical links between the CPU and an external memory bank, then all memory becomes cache. This could fundamentally change the way we design High Performance Computing systems.SIlicon Photonics transceivers for datacenter applications are already shipping in volume (many million units per year), so we are starting to understand and hone electronics-photonics integration on a silicon platform (see Intel Silicon Photonics).MEMs devices like tiny gyroscopes, electro-mechanical mirrors, mechanical resonators can be very helpful in making devices for advanced navigation because you can directly integrate the sensors and the electronics and logic needed to drive the sensors into a very tiny package due to heterogeneous integration.The ultimate example of heterogeneous integration that is being worked on today is or compact LiDAR systems. Current LiDAR systems are expensive and bulky due to poor integration of electronics and optics. A heterogeneously integrated LiDAR chip, on the other hand, will have: (a) photonics components like lasers, optical amplifiers, photodetectors, optical modulators, and (b) electrical driver and receiver circuits for the optical components, as well as electrical logic circuits, and (c) MEMs devices like tunable mirrors and reflectors to steer the beam of light. And all of this will be integrated in a package with a small form factor.Most of the progress in semiconductors over the past few decades has been in the electrical logic technology, and now the tech is finally getting to the point where heterogeneous integration starts to look technologically necessary and economically viable. This technology opens up and entire new world for chip and device designers.

According to this 10  Gb/s optical random access memory (RAM) cell :Optical random access memories (RAMs) have been conceived as high-bandwidth alternatives of their electronic counterparts, raising expectations for ultra-fast operation that can resolve the ns-long electronic RAM access bottleneck. However, experimentally demonstrated optical RAMs have been limited to up to 5 GHz only, failing to validate the speed advantages over electronics.In this Letter, we demonstrate the first all-optical RAM cell that performs both Write and Read functionalities at 10 Gb/s, reporting on a 100% speed increase compared to state-of-the-art optical RAM demonstrations.To achieve this, the proposed RAM cell deploys a monolithically integrated InP optical Flip-Flop and a Semiconductor optical amplifier-Mach–Zehnder Interferometer (SOA-MZI) On/Off switch configured to operate as a strongly saturated differentially-biased access gate.Error-free operation is demonstrated at 10 Gb/s for both Write and Read operations with 6.2 dB and 0.4 dB power, respectively, achieving the fastest reported RAM cell functionalities.Congratulations to everyone involved.If someone knows whether there is commercial applicability (i.e. mass production in the near future) please drop a comment.

The process of communicating using fiber-optics involves the following basic steps:Creating the optical signal involving the useof a transmitter, relaying the signal alongthe fiber, ensuring that the signal does notbecome too distorted or weak, receiving theoptical signal, and converting it into anelectrical signal .Fiber Optic CableFiber optic cabling is based on optical fibers,which are long, flexible, hair-width strands ofultra-pure glass. Optical fibers are formed whenpreform blanks – portions of speciallymanufactured glass – are heated to between3000 and 4000 degrees and then drawn out at arate of up to 66 feet per second. As optical fiberis pulled, it is constantly monitored by a lasermicrometer, which ensures that its diameter isperfectly uniform from start to finish.In order for optical fibers to transmit data overlong distances, they need to be highly reflective.On their way to being spooled, newly-pulled glassfibers pass through coating cups and ultravioletovens , which respectively apply and then curethe thin plastic buffer coating that creates amirror effect within the fiber.The finished optical fiber is then extensivelytested in a wide range of categories, includingTensile Strength, Refractive Index Profile, FiberGeometry, Attenuation, Bandwidth, ChromaticDispersion, Operating Temperature, TemperatureDependence of Attenuation, and Ability to ConductLight Underwater. After testing has proven thatthe newly-manufactured optical fiber meets allstandards, it is sold for use in fiber optic cabling.Depending on what type of application it will beused for and how much data it will need totransmit, fiber optic cable can be built around asingle strand of optical fiber, or larger groupingsof it. To assemble a complete fiber optic cable,the strand or cluster of optical fiber is placed atthe core, to be surrounded by a loose tube ofPVC, which leaves the fiber room to bend whenbeing routed around corners and through conduit.The loose PVC is then covered with a layer ofshock-absorbing aramid yarn – usually made ofKevlar. To top it all off, the cable receives a finalouter-jacket coating of PVC, which helps to sealout moisture.In order for the finished cable to transmit datasignals, it needs to be connected to the twoother main components of a fiber-optic system.The first of these is the optical transmitter , adevice which converts electrical and analogsignals into either On-Off or Linear modulatinglight signals, then releases that data into thefiber optic cable. The cable then relays the dataemitted by the optical transmitter to the opticalreceiver , which accepts the light signal andreformats the data into its original form.Optical transmitterThe most commonly used optical transmittersare semiconductor devices such as light-emitting diodes (LEDs) and laser diodes . Thedifference between LEDs and laser diodes isthat LEDs produce incoherent light , while laserdiodes produce coherent light . For use inoptical communications, semiconductoroptical transmitters must be designed to becompact, efficient, and reliable, whileoperating in an optimal wavelength range, anddirectly modulated at high frequencies.In its simplest form, a LED is a forward-biasedp-n junction, emitting light throughspontaneous emission, a phenomenon referredto as electroluminescence. The emitted lightis incoherent with a relatively wide spectralwidth of 30-60 nm. LED light transmission isalso inefficient, with only about1% of input power, or about100 microwatts, eventually converted intolaunched power which has been coupled intothe optical fiber. However, due to theirrelatively simple design, LEDs are very usefulfor low-cost applications.Communications LEDs are most commonlymade from Indium gallium arsenide phosphide(InGaAsP) or gallium arsenide (GaAs).Because InGaAsP LEDs operate at a longerwavelength than GaAs LEDs (1.3 micrometersvs. 0.81-0.87 micrometers), their outputspectrum, while equivalent in energy is widerin wavelength terms by a factor of about 1.7.The large spectrum width of LEDs is subjectto higher fiber dispersion, considerably limitingtheir bit rate-distance product (a commonmeasure of usefulness). LEDs are suitableprimarily for local-area-network applicationswith bit rates of 10-100 Mbit/s andtransmission distances of a few kilometers.LEDs have also been developed that useseveral quantum wells to emit light atdifferent wavelengths over a broad spectrum,and are currently in use for local-area WDM(Wavelength-Division Multiplexing) networks.Today, LEDs have been largely superseded byVCSEL (Vertical Cavity Surface EmittingLaser) devices, which offer improved speed,power and spectral properties, at a similarcost. Common VCSEL devices couple well tomulti mode fiber.A semiconductor laser emits light throughstimulated emission rather than spontaneousemission, which results in high output power(~100 mW) as well as other benefits relatedto the nature of coherent light. The output ofa laser is relatively directional, allowing highcoupling efficiency (~50 %) into single-modefiber. The narrow spectral width also allowsfor high bit rates since it reduces the effect ofchromatic dispersion . Furthermore,semiconductor lasers can be modulateddirectly at high frequencies because of shortrecombination time.Commonly used classes of semiconductorlaser transmitters used in fiber optics includeVCSEL (Vertical-Cavity Surface-EmittingLaser), Fabry–Pérot and DFB (DistributedFeed Back).Laser diodes are often directly modulated ,that is the light output is controlled by acurrent applied directly to the device. For veryhigh data rates or very long distance links , alaser source may be operated continuouswave , and the light modulated by an externaldevice such as an electro-absorptionmodulator or Mach–Zehnder interferometer .External modulation increases the achievablelink distance by eliminating laser chirp , whichbroadens the linewidth of directly modulatedlasers, increasing the chromatic dispersion inthe fiber.Optical ReceiverThe main component of an optical receiver isa photodetector , which converts light intoelectricity using the photoelectric effect . Theprimary photodetectors fortelecommunications are made from Indiumgallium arsenide The photodetector istypically a semiconductor-based photodiode .Several types of photodiodes include p-nphotodiodes, p-i-n photodiodes, and avalanchephotodiodes. Metal-semiconductor-metal(MSM) photodetectors are also used due totheir suitability for circuit integration inregenerators and wavelength-divisionmultiplexers.Optical-electrical converters are typicallycoupled with a transimpedance amplifier anda limiting amplifier to produce a digital signalin the electrical domain from the incomingoptical signal, which may be attenuated anddistorted while passing through the channel.Further signal processing such as clockrecovery from data (CDR) performed by aphase-locked loop may also be applied beforethe data is passed on.