All-Optical Digital Circuits Exploiting SOA-Based Loop Memories

Optical RAM and integrated optical memories: a survey

“…Optical memories based on feedback loops, shown in Fig. 2b, require a single active component along with an external cavity usually implemented by loop configurations that feed the output signal back to the active element either through a fiber 26,27,48,49 or by using an integrated bent waveguide 36 . The cavity acts as the memory element, enabling bit storage, and a tap of the cavity allows for monitoring the logical state of the feedback loop, i.e., the memory content.…”

“…Optical volatile memories can typically offer faster access times and higher speed operation compared to their non-volatile counterparts and form the core memory mechanism in the optical versions of the well-known and highly useful RAM cell architectures, again discriminated into two main categories: (a) the optical dynamic (DRAM) and (b) the optical static (SRAM) RAM, with their main difference lying in their requirement for refreshing (DRAM) or not (SRAM) the stored bit value. Optical SRAM layouts have thus far been implemented mainly by means of bistable optical devices , whereas the optical DRAM cells that have been reported rely on either lowspeed optical physical mechanisms such as ion excitation [44][45][46][47] or recirculating loop arrangements 48,49 . Optical non-volatile memories are a more recent addition to lightenabled memory technology, mainly taking advantage of the rapid progress experienced in the field of phasechange material (PCM) structures [50][51][52][53][54][55] , which have been shown to allow for permanent light storage in a continuously growing field of diverse applications.…”

All-Optical Phase Memory Circuit Based on Two Coupled Lasers and External Optical Injection

“…Analogously to the electronic memory circuits, optical bit-level memories can be divided into two categories: dynamic and static, depending on the presence or absence of the required memory state refreshing, respectively. Various schemes have been studied for optical dynamic memory capabilities, such as optical buffers based on recirculating loops [16], bistable systems based on absorption and transparency [17], [18], and electroluminescence [19] in a rare-earth-doped medium.…”

All-Optical XOR Gate Using Single Quantum-Dot SOA and Optical Filter

“…In particular, the XOR gate is mostly indispensable for this purpose because it is involved in the accomplishment of many signal processing tasks entirely in the optical domain. These include packet processing [2], [3], pseudorandom binary sequence generation [4], [5], encryption/decryption [6], error detection and correction [7], arithmetic operations [8], [9], construction of optical memory elements [10], and digital comparison [11], [12]. Given the importance of XOR gate and that single channel data rates are being upgraded to cope with bandwidthhungry applications [1], intense research efforts have been made to realize the XOR gate at 160 Gb/s and beyond.…”