High speed all-optical PRBS generation based on quantum-dot semiconductor optical amplifiers

Abstract

A scheme to generate return-to-zero on-off keying (RZ-OOK) high speed all-optical pseudo random bit sequence (PRBS) based on quantum-dot semiconductor optical amplifiers (QD SOA) has been studied. By analyzing the performance of the core functional unit of this system, which is composed of QD SOA-based logic XOR and AND gates, as well as considering the saturation effect of the QD device and noise level of the system, we demonstrated the system's capability of producing stable high speed optical PRBS signals. Results show that the performance of the system depends on a number of parameters, including relaxation lifetime from QD excited state to ground state, injected current density, bit repetition rate, signal pulse width and single pulse energy. For devices with relaxation time approximately 1.0 ps, injected current density >1.8 kA/cm(2), single pulse energy <1.0 pJ with pulse width around 1.0 ps, the system is capable of PRBS generation at speeds of approximately 250 Gb/s.

High speed all-optical PRBS generation using binary phase shift keyed signal based on QD-SOA

“…Parameters chosen for simulation in this work are experimental results on QD-SOAs for central wavelength: 1.55μm: τ wr =τ esr =200ps, τ gsr =50ps, τ w-e =3ps, τ e-w =300ps [25], τ g-e =10ps, Γ d =10%, linewidth enhancement factors α=4, α CH =0.2 [23,24], QD energy levels' densities of states, n w =5.4×10 17 cm -3 , n w :n e :n g ≈15:2:1 [20], QD areal density is 7.5×10 10 cm -2 , saturated output power is 18dBm at 1.55μm wavelength [17], device differential gain a=8.6×10 -15 cm 2 [16], effective length l=1.0mm, noise figure F=7dB [17], transparency pump current density is ~0.2kA/cm 2 [21], gain suppression factors are ε CH =0.5×10 -23 m 3 , ε SHB =7.5×10 -23 m 3 [26], which correspond to threshold input pulse energy for both nonlinear effects ~0.47pJ, Value of time constant τ e-g has been measured in many experiments, the smallest report value is ~0.1ps [21] and the largest measured value goes up to several picoseconds [18]. We have not taken into account the inhomogeneous broadening associated with different dot sizes.…”

High speed all-optical encryption and decryption using quantum dot semiconductor optical amplifiers

“…Parameters chosen for simulation in this work are experimental results on QD-SOAs for central wavelength: 1.55 μm: τ wr = τ esr = 200 ps, τ gsr = 50 ps, τ w-e = 3 ps, τ e-w = 300 ps [28], τ g-e = 10 ps, Γ d = 10%, linewidth enhancement factors α = 4, α CH = 0.2 [26,27], QD energy levels' densities of states, n w = 5.4 × 10 17 cm −3 , n w : n e : n g ≈ 15 : 2 : 1 [23], QD areal density is 7.5 × 10 10 cm −2 , saturated output power is 18 dBm at 1.55 μm wavelength [20], device differential gain a = 8.6 × 10 −15 cm 2 [19], effective length l = 1.0 mm, noise figure F = 7 dB [20], transparency pump current density is~0.2 kA/cm 2 [24], gain suppression factors are ε CH = 0.5 × 10 −23 m 3 , ε SHB = 7.5 × 10 −23 m 3 [29], which correspond to threshold input pulse energy for both nonlinear effects~0.47 pJ. The value of time constant τ e-g has been measured in many experiments; the smallest reported value is~0.1 ps [24] and the largest measured value goes up to several picoseconds [21].…”

Simultaneous all-optical basic arithmetic operations using QD-SOA-assisted Mach–Zehnder interferometer

“…The carrier transitions between various states in the QDSOAs are described by the following rate equations [10,16,[23][24][25][26][27][28][29]:…”