I. Shubin

High-power intrastep quantum well electroabsorption modulator using single-sided large optical cavity waveguide

A novel electroabsorption modulator (EAM) using intrastep quantum wells (IQWs) and a single-sided large optical cavity waveguide is demonstrated to operate at up to 100 mW of input optical power. When the IQW EAM with uncoated facets is tested in an analog fiber link, the radio-frequency link gain reaches -16.1 dB at 100-mW optical power. We have measured a single-octave spurious-free dynamic range (SFDR) of 121 dB/spl middot/Hz/sup 4/5/ and multioctave SFDR of 110 dB/spl middot/Hz/sup 2/3/ for this EAM.

Gain Limit in Analog Links Using Electroabsorption Modulators

Analog optical links using electroabsorption modulators have a gain limit caused by the photocurrent in the modulator. The gain limit results in a minimum link noise figure as well. The gain limit is due to the voltage-dependent absorption causing a voltage-dependent component to the photocurrent; the gain limit applies to a modulator that has this relationship

Analysis of linearity of highly saturated electroabsorption modulator link due to photocurrent feedback effect.

We have analyzed the linearity performance of analog fiber-optic links based on electroabsorption modulators (EAM) operating at high optical power. The negative feedback caused by photocurrent generation improves the modulator linearity in the gain saturation regime. In the absence of laser relative intensity noise (RIN), the link spur-free dynamic range (SFDR) increases with the power of four-thirds of the input optical power after gain saturation occurs. A multi-octave SFDR of more than 135 dB/Hz2/3 has been found to be achievable with sufficiently high power.

High Power MQW Electroabsorption Modulator with a Waveguide Taper

Peripheral coupled waveguide (PCW) electro-absorption modulator (EAM) with different dimensions is studied. By incorporating a waveguide taper in the PCW to reduce the absorption at the input facet of the EAM, we show that the saturation effect due to high current density can be reduced.

Characterization of an electroabsorption modulator design with high-dynamic range for broadband analog applications

An electroabsorption modulator (EAM) is designed to optimize dynamic range performance over 20 GHz bandwidth. The single stripe waveguide enables an extremely compact and integrated package to be fabricated with single mode fiber pigtails. The transfer functions shape permits suppression of higher order intermodulation products, yielding a spur-free dynamic range exceeding that of Mach- Zehnder designs. A dilute optical core diverts energy flow from absorbing layers into low loss waveguide; the 20 dBm optical power tolerance is significantly higher than that of commercially available electroabsorption devices. The tunable performance over 20 GHz is characterized and applications are discussed. New approaches to the broadband impedance matching requirements are calculated and the impact on system performance is assessed.

Transparent ROF link using EA modulators

Transparent analog fiber link is the key element to many radio-over-fiber applications such as antenna remoting and CATV. In this paper, we present the performance of analog fiber link using advanced design of electroabsorption modulator that incorporates peripheral coupled waveguide (PCW) and intra-step-barrier quantum well (IQW) designs. High efficiency PCW-IQW electroabsorption modulator with high optical power handling property will be presented. The resultant transparent analog fiber link can be used for achieving high spurious free dynamic range.

Design and development of a package for a diluted waveguide electro-absorption modulator

Externally coupled electroabsorption modulators (EAM) are commonly used in order to transmit RF signals on optical fibers. Recently an alternative device design with diluted waveguide structures has been developed. [1] Bench tests show benefits of lower propagation loss, higher power handling (100 mW), and higher normalized slope efficiency. This paper addresses the specific issues involved in packaging the diluted waveguide EAM devices. An evaluation of the device requirements was done relative to the standard processes. Bench tests were performed in order to characterize the optical coupling of the EAM. The photo current maximum was offset from the optical power output maximum. The transmissions vs. bias voltage curves were measured, and an XY scanner was used to record the mode field of the light exiting from the EAM waveguide in each position. The Beam Propagation Method was used to simulate the mode field and the coupling efficiency. Based on the bench tests and simulation results, a design including mechanical, optical and RF elements was developed. A Newport Laser Welding system was utilized for fiber placement and fixation. The laser welding techniques were customized in order to meet the needs of the EAM package design.

Saturation Effect of Electroabsorption Modulator on Analog Link Gain and Linearity

The linearity and link gain performance of analog fiber-optic links based on electroabsorption modulators operating at high optical power is analyzed. The negative feedback attributed to the photocurrent generation improves the modulator linearity at high optical power while causes the link gain to saturate. Potential schemes to improve both will be presented.

High Power Electroabsorption Waveguide Device

We demonstrate here a dual function electroabsorption waveguide device that operates as a modulator in the receiving mode and a detector in the transmitting mode in the case of antenna remoting application. Both electroabsorption modulator (EAM) and photodetector (PD) are known to saturate at high optical inputs as a result of space-charge carrier screening in the EAM modulating or PD absorbing depletion region as well as from the inadequate thermal power dissipation. Our device is designed to operate at high levels of incident input optical power. In the photodetector mode it sustained 590 mW of optical input power and generated 222 mA of output current. To our knowledge it is the highest current demonstrated for a single mode waveguide photodetector

High-power and high-linearity traveling wave electroabsorption modulator

Design for high efficiency, high power traveling wave electroabsorption modulator using Intra-Step-Barrier Quantum Well (IQW) and Peripheral Coupled waveguide (PCW) designs are presented. Both of these designs have separately yielded EAMs with high optical power handling and low Vp properties, in an analog fiber link configuration. The IQW EAM has low Vp (~0.73 V) and high power handling (100 mW). The lumped element IQW EAM has achieved a link gain of -16 dB, a multi-octave SFDR of 110 dB-Hz2/3 and a single-octave SFDR of 121dB-Hz4/5 at the 1543 nm wavelength. The PCW MQW EAM with lumped element configuration can achieve a low link low, a high multi-octave SFDR at the same wavelength. The traveling wave properties of these EAMs are under investigation.