E.J. Jansen

Reduced intermodulation distortion in 1300 nm gain-clamped MQW laser amplifiers

A 1300 nm gain-clamped DFB multiple quantum well laser amplifier with negligible pass band ripple, 20 dB fiber to fiber gain, and 10 dB reduction in gain saturation is demonstrated. The remaining gain saturation is attributed to longitudinal hole burning. After some modifications the reduction in gain saturation is improved to more than 30 dB for an input signal having the same polarization state as the lasing mode. From these experiments and a theoretical analysis it is concluded that there is a potential for realizing highly linear 1300 nm CATV semiconductor laser amplifiers using gain-clamping with less intermodulation distortion than todays directly modulated linear semiconductor lasers.<<ETX>>

A compact nine-channel multiwavelength laser

A phased-array-based multiwavelength laser has been realized on a chip area of 3.5/spl times/2.5 mm/sup 2/. The device has nine channels, spaced at 400 GHz around a central wavelength of 1.55 /spl mu/m. Its performance is characterized by a minimum threshold current of 101 mA, a maximum fiber-coupled power of 0.37 mW, and a linewidth of 21 MHz. In addition, simultaneous four-channel operation is demonstrated.

Polarization resolved, complete characterization of 1310 nm fiber pigtailed multiple-quantum-well optical amplifiers

A new method allowing an automated, polarization resolved, complete characterization of fiber pigtailed semiconductor optical amplifiers is presented and discussed. The method is applied to a high performance, polarization insensitive 1310 nm strained layer multiple-quantum-well semiconductor optical amplifier. For this amplifier 36 dB fiber to fiber gain, a 3 dB gain saturation output power of 15 dBm and a noise figure of 6.5 dB are demonstrated and the polarization dependence of these key performance figures is clarified. The result is presented in a form which should enable the end-user to derive realistic performance figures which will be obtained for a fluctuating random input signal state of polarization.

High-gain 1310 nm semiconductor optical amplifier modules with a built-in amplified signal monitor for optical gain control

A compact high-gain 1310-nm semiconductor optical amplifier (SOA) module incorporating two photodiodes to detect radiation emitted from the two opposite facets of the amplifier chip is reported. By subtracting their signals, a measure of the amplified signal is obtained without the need for optical filtering, Using this, amplified signals can be stabilized within 0.5 dB over a 25-dB range of input signals.

27-dB gain unidirectional 1300-nm polarization-insensitive multiple quantum well laser amplifier module

An unidirectional polarization-insensitive multiple quantum well laser amplifier module for the 1300-nm window with a record high gain of 27 dB and a 3-dB saturation output power of 13 dBm is demonstrated. The module gain has a 3-dB width exceeding 60 nm and shows a typical polarization sensitivity and gain ripple as low as 0.3 dB. To provide immunity for backscattered or reflected light, polarization independent optical isolators were inserted in the input and output coupling optics of the package. A practical optical amplifier module for the 1300-nm window is very desirable, because most of the presently installed fiber has its zero dispersion wavelength around 1310 mm, while much of the older fiber often only can be operated around this wavelength.<<ETX>>

1310-nm DBR-type MQW gain-clamped semiconductor optical amplifiers with AM-CATV-grade linearity

A 1310-nm gain clamped semiconductor optical amplifier with amplitude modulation CATV-grade linearity at an output power of 8 mW is demonstrated for the first time. The InGaAsP multiquantum-well laser amplifier is equipped with distributed Bragg reflectors at each end to supply the feedback necessary for gain clamping. The TE optical gain of 21.3 dB is measured to be constant within 0.1 dB up to 25-mW signal output power. Electrical signal distortion experiments are presented to demonstrate the linearity of the device.

Loss reduction for phased-array demultiplexers using a double etch technique

Wavelength Division Multiplexing (WDM) is an effective technique to exploit the huge bandwidth of optical fibres. Key components in such WDM-systems are demultiplexers which spatially separate the different wavelength channels. Phased-array demultiplexers combine ease of fabrication and low insertion losses. Silica-based phased-array demultiplexers are realised with low losses from 2-3 dB [1,2]. InP-based demultiplexers show slightly higher on-chip losses of 4-6 dB [3,4]. In addition they have considerably higher fibre coupling losses (several dB’s), but the advantage of InP-based demultiplexers is that they can be integrated with active components. Earlier we reported a low-loss demultiplexer with reduced fibre coupling loss by applying deeply etched InGaAsP waveguides with a relatively large core and a low index contrast, which had an almost circular mode profile [5]. The component had 4-5 dB on-chip loss and fibre coupling loss of about 1 dB to a tapered fibre. In this article we report a method to further reduce the on-chip losses.

Wavelength-independent output power from an injection-tunable DBR laser

Injection-tunable three-section distributed Bragg reflector lasers emitting near 1.55 /spl mu/m have been fabricated employing bulk 1.48-/spl mu/m-bandgap InGaAsP in the tuning layer of the phase and Bragg sections. The gain in this material compensates for the increased absorption loss during tuning, which results in a nearly wavelength-independent optical output power. The maximum obtained output power is 28 mW ex facet, with a spectral linewidth around 5 MHz.<<ETX>>

High-output-power (+15 dBm) unidirectional 1310-nm multiple-quantum-well booster amplifier module

A unidirectional multiple-quantum-well booster amplifier module for the 1310-nm transmission window with a high 3-dB gain saturation output power of 18 dBm and a fiber-to-fiber gain of 17 dB is demonstrated. The module is equipped with a polarization-maintaining input fiber and optical isolators have been included. The booster amplifier was tested with a 1310-nm DFB laser directly modulated at 10 Gb/s, showing that 14.6 dBm of average fiber-launched output power could be obtained at 1 dB BER penalty, and that power budgets of 26.8 dB and 39.4 dB could be realized for a PIN photodiode receiver and an optically preamplified receiver, respectively, making repeaterless 10 Gb/s transmission over 70 to 100 km of standard single-mode optical fiber at 1310 nm a practical option.

High-gain 1310-nm reflective semiconductor optical amplifiers with low-gain uncertainty

A 1310-nm reflective semiconductor optical amplifier with a gain uncertainty of only 0.8 dB at an average gain level of over 30 dB has been demonstrated using a microoptic polarization reversing retroreflector. For this amplifier 3-dB saturation output powers of up to 10 dBm and a noise figure of 7.5 dB have been obtained. A low gain uncertainty for undefined input signal polarization states and input signal wavelengths (which may vary over several nanometers) is of primary importance in switching applications.