P.A. Andrekson

Mode-locked hybrid soliton pulse source with extremely wide operating frequency range

The authors report a mode-locked pulse source with extremely wide operating frequency range and very stable operation, through the use of a long, linearly chirped Bragg reflector as the output coupler integrated in a fiber external cavity. A 1.55 mu m strained MQW laser diode is used, with one facet high reflectivity (HR) coated for improved cavity Q, and the other antireflection (AR) coated to allow coupling to the external cavity and suppress Fabry-Perot modes. Near-transform-limited pulses are obtained over a frequency range of 700 MHz around a system operating frequency of 2.488 GHz, with pulsewidths of 50 ps, as required for a practical soliton transmission system.<<ETX>>

64 Gb/s all-optical demultiplexing with the nonlinear optical-loop mirror

The first complete nonlinear optical-loop mirror demultiplexing experiments including error-rate measurements are reported. Broadband demultiplexing of 16-, 32-, and 64-Gb/s, 2/sup 15/-1 data was performed using only semiconductor lasers. The penalty for demultiplexing a 64-Gb/s time-division multiplexed data stream to the 4-Gb/s fundamental rate was 2.2 dB at an error rate of 10/sup -9/. The switching pulse energy was 1.1 pJ.<<ETX>>

32 Gb/s optical soliton data transmission over 90 km

The authors demonstrate error-free optical soliton transmission at 32 Gb/s over 90 km of dispersion-shifted fiber. Fiber loss was compensated for by using diode laser pumped Er/sup 3+/-doped fiber amplifiers located every 30 km and a 4 Gb/s data pattern was passively multiplexed to 32 Gb/s. Approximately 16-ps-wide, near transform-limited pulses were launched into the system and the output pulsewidth was about 14 ps. At the receiver, four-wave mixing was employed to perform all optical demultiplexing of the data down to the base data rate. At a 10/sup -9/ (2/sup 15/-1 word length) bit-error rate, the penalties from the demultiplexing and the 90-km soliton transmission were approximately 1.6 and 0.5 dB, respectively.<<ETX>>

Effect of thermionic electron emission from the active layer on the internal quantum efficiency of InGaAsP lasers operating at 1.3 /spl mu/m

We have experimentally characterized the quantum efficiency in InGaAsP lasers operating at 1.3 /spl mu/m. The observed reduction in external quantum efficiency with increasing temperature and increasing bias current is found to be caused almost entirely by a reduction of the internal quantum efficiency. The internal quantum efficiency is reduced approximately linearly with bias current in the temperature range investigated. The experimental results are well explained with a theoretical model based on thermionic emission of carriers out of the active region. >

Observation of multiple wavelength soliton collisions in optical systems with fiber amplifiers

Solitons of different wavelengths are found to exhibit substantial spectral and temporal changes when collisions are centered in erbium‐doped fiber amplifiers. By using two soliton pulse trains, with ∼70‐ps‐wide pulses, spectrally separated by 1.8 A, and 106 km of non‐dispersion‐shifted fiber, we observe a spectral and temporal shift of as much as 0.35 A and 55 ps, respectively, for each soliton. Both soliton wavelengths shift the same amount, but in opposite directions and remain undisturbed in terms of shape and amplitude after the collision. This shift may impose limitations on multiple wavelength soliton based communication systems utilizing fiber amplifiers.

Observation of collision induced temporary soliton carrier frequency shifts in ultra-long fiber transmission systems

Multiwavelength soliton interaction over 10000 km in an Er/sup 3+/-doped fiber amplifier based system is studied in a fiber loop configuration. Collisions that takes place over distances significantly longer than amplification period are found to produce nonpermanent shifts of the soliton carrier frequencies, thus acting as collisions in a lossless medium. The spectral shift is found to be inversely proportional to the wavelength separation and is reduced with increasing pulse width. The effects of these unavoidable collisions will impose a limit on the minimum channel spacing in ultra-long-haul soliton based communication systems. >

4 Gb/s soliton data transmission over 136 km using erbium doped fiber amplifiers

The use of semiconductor-laser-pumped erbium-doped fiber amplifiers and an externally modulated mode-locked external-cavity semiconductor laser to obtain soliton data transmission at 4 Gb/s over 136 km of nondispersion shifted fiber is described. After 136 km of transmission and at low pulse powers, the approximately 80 ps fiber input pulse width was broadened to approximately 150 ps. At high pulse powers the output pulse width was maintained at 80 ps, as expected for N=1 solitons. N=3 solitons were also observed at lower data rates.<<ETX>>

DFB lasers with monolithically integrated passive waveguide

Novel MQW integrated passive waveguide (IPW) DFB lasers have been fabricated using a selective area MOVPE growth technique. Detailed measurements of the absorption loss of the passive waveguide in the structure as well as its influences on the laser linewidth are reported for the first time. A linewidth reduction factor of more than 3 is observed as compared to a simple DFB laser despite the high absorption loss.<<ETX>>

High power semiconductor laser injection-locking at 1.3 mu m

The injection-locking properties of a high power antireflection coated 1.3- mu m slave laser subjected to relatively low injection powers from a distributed feedback (DFB) laser and from a tunable external cavity laser have been investigated. Narrow linewidth operation ( approximately 40 kHz) was demonstrated and the tuning range within two slave modes ( approximately 10 GHz) and over the gain profile ( approximately 40 nm) was investigated. In addition, the tracking properties of the slave laser for both frequency and phase modulated injected light was evaluated at 1 Gb/s, in which the fidelity was judged from bit-error-rate measurements. The maximum locked power under 1 Gb/s frequency modulation was about 145 mW, limited by the available master power; approximately 300 mu W was injected into the slave. >

Spectral linewidth of multiple quantum well distributed feedback (MQW-DFB) lasers grown by low pressure MOVPE

The authors investigate the dependence of the spectral linewidth of strained MQW-DFB (multiquantum-well distributed-feedback) lasers on device parameters, such as coupling strength and the number of quantum wells. The spectral linewidth of the MQW-DFB lasers is compared to that of a bulk active laser, as well as to that of a novel MQW-DFB laser with a monolithically integrated passive waveguide. The spectral linewidth of the strained MQW lasers was found to be less than that of the bulk active DFB lasers. Further reduction in the spectral linewidth was observed for MQW structures with a fewer number of wells and larger detuning of the Bragg wavelength. However, the monolithically integrated passive waveguide DFB structure was found to improve the spectral linewidth to a greater extent than conventional strained MQW-DFB lasers.<<ETX>>