Dr. Heinz A. Willebrand Profile

Dr. Heinz A. Willebrand

CTO

SPIE Involvement:

Author

Proceedings Article | 30 April 2003 Paper

Reliability issues of free-space communications systems and networks

Heinz Willebrand

Proceedings Volume 4940, (2003) https://doi.org/10.1117/12.477408

KEYWORDS: Free space optics, Visibility, Signal attenuation, Sensors, Vertical cavity surface emitting lasers, Reliability, Telecommunications, Visibility through fog, Absorption, Semiconductor lasers

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Proceedings Article | 9 December 2002 Paper

Free-space optics system operation in Asian cities under heavy-dust-loading conditions

Olga Kalashnikova, Heinz Willebrand

Proceedings Volume 4821, (2002) https://doi.org/10.1117/12.450624

KEYWORDS: Particles, Atmospheric particles, Atmospheric modeling, Refractive index, Atmospheric optics, Optical properties, Free space optics, Minerals, Visibility, Visible radiation

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Until recently atmospheric dust was not a major concern for free-space optics communication systems, however the heavy pollution and the recent increase in dust-storm events in Asia and particularly in China, has motivated the studies we present in this paper. In this paper we will discuss the impact of dust on free-space optics system operations for transmission wavelengths up to 10μm. We focus our studies on China as dust is normally present in its lower atmospheric regions, and since dust originating in China is transported over most of Asia during heavy dust storms. In general, heavy dust loadings consists of larger dust particles that are lifted from the ground and whose atmospheric concentrations can reach values that are high enough to interrupt the operation of free-space optics communication links. Similar to the characterization of fog conditions, dust storm studies are usually based on visibility data. However, in the case of mineral dust, visibility data are not sufficient to accurately predict the impact of dust on atmospheric transmissions. Transmission coefficients during dusty days cannot be simply calculated from visibility data for the entire range of useful laser wavelengths due to complex wavelength dependencies on mineral dust refractive indices. In order to test laser operating conditions in China, we ran extensive MODTRAN calculations of atmospheric transmissions for different dust conditions in the visible-IR range. Wavelength-dependent optical properties of atmospheric dust, which are required as input to the MODTRAN dust models, were calculated via Mie theory (spherical dust) using representative dust morphological and mineralogical properties such as refractive indices, size distributions and concentrations. We also tested an effect of particle nonsphericity at several wavelengths. We found that the effect of non-sphericity is small for direct beam transmissions, thought, it may become an important factor for diffused forward-scattered radiation. We found that changes in dust particle concentrations and dust particle size distributions during dust-storms storngly affect the transmission in the entire visible and IR wavelength range.

Proceedings Article | 26 April 2002 Paper

Wavelength and altitude dependence of laser beam propagation in dense fog

Olga Kalashnikova, Heinz Willebrand, Laurel Mayhew

Proceedings Volume 4635, (2002) https://doi.org/10.1117/12.464103

KEYWORDS: Fiber optic gyroscopes, Signal attenuation, Atmospheric particles, Visibility through fog, Visibility, Particles, Scattering, Laser scattering, Mie scattering, Atmospheric propagation

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Proceedings Article | 5 December 2001 Paper

Scintillation bit error rate-reduction for free space optical communications systems

Heinz Willebrand, Erhard Kube, Laurel Mayhew

Proceedings Volume 4441, (2001) https://doi.org/10.1117/12.449562

KEYWORDS: Scintillation, Receivers, Transmitters, Telecommunications, Signal attenuation, Free space optical communications, Infrared lasers, Optical communications, Fiber optic gyroscopes, Information operations

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Proceedings Article | 27 November 2001 Paper

Local multipoint distribution system (LDMS) versus free-space optical (FSO) networks

Gerald Clark, Bryan Willson, Heinz Willebrand, Laurel Mayhew, Christian Andreu von Euw, Joe Roy

Proceedings Volume 4530, (2001) https://doi.org/10.1117/12.449813

KEYWORDS: Free space optics, Signal attenuation, Laser scattering, Scattering, Antennas, Fiber optic gyroscopes, Atmospheric propagation, Free space, Scintillation, Atmospheric optics

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Proceedings Article | 18 October 2001 Paper

Free space optics: a viable last-mile alternative

Gerald Clark, Heinz Willebrand

Proceedings Volume 4586, (2001) https://doi.org/10.1117/12.445229

KEYWORDS: Free space optics, Optical networks, Buildings, Networks, Network architectures, Fiber optics, Fiber optic gyroscopes, Telecommunications, Standards development, Laser safety

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This paper explores Free Space Optics (FSO) as an access technology in the last mile of metropolitan area networks (MANs). These networks are based in part on fiber-optic telecommunications infrastructure, including network architectures of Synchronous Optical Network (commonly referred to as SONET), the North American standard for synchronous data transmission; and Synchronous Digital Hierarchy (commonly referred to as SDH), the international standard and equivalent of SONET. Several converging forces have moved FSO beyond a niche technology for use only in local area networks (LANs) as a bridge connecting two facilities. FSO now allows service providers to cost effectively provide optical bandwidth for access networks and accelerate the extension of metro optical networks bridging what has been termed by industry experts as the optical dead zone. The optical dead zone refers to both the slowdown in capital investment in the short-term future and the actual connectivity gap that exists today between core metro optical networks and the access optical networks. Service providers have built extensive core and minimal metro networks but have not yet provided optical bandwidth to the access market largely due to the non-compelling economics to bridge the dead zone with fiber. Historically, such infrastructure build-out slowdowns have been blamed on a combination of economics, time-to-market constraints and limited technology options. However, new technology developments and market acceptance of FSO give service providers a new cost-effective alternative to provide high-bandwidth services with optical bandwidth in the access networks. Merrill Lynch predicts FSO will grow into a $2 billion market by 2005. The drivers for this market are a mere 5%- 6% penetration of fiber to business buildings; cost effective solution versus RF or fiber; and significant capacity which can only be matched by a physical fiber link, Merrill Lynch reports. This paper will describe FSO technology, its capabilities and its limitations. The paper will investigate how FSO technology has evolved to its current stage for deployment in MANs, LANs, wireless backhaul and metropolitan network extensions - applications that fall within the category of last mile. The paper will address the market, drivers and the adoption of FSO, plus provide a projection of future FSO technology, based on today's product roadmaps. The paper concludes with a summary of findings and recommendations.

Proceedings Article | 6 February 2001 Paper

Wireless optics protection of fiber via SONET ring closure

Ruth Ann Mullen, Michael Kefauver, Doug Carter, Jared Miller, Ken Celmer, Jimmie Wooten, Maha Achour, Michael Foster, Heinz Willebrand, John Kean, Bhupendra Singh

Proceedings Volume 4214, (2001) https://doi.org/10.1117/12.417510

KEYWORDS: Free space optics, Atmospheric optics, Switching, Visibility, Switches, Relays, Visibility through fog, Signal attenuation, Fiber lasers, Fiber optic gyroscopes

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Proceedings Article | 6 February 2001 Paper

Hybrid free-space optical/microwave communication networks: a unique solution for ultrahigh-speed local loop connectivity

Heinz Willebrand, Gerald Clark, Maha Achour

Proceedings Volume 4214, (2001) https://doi.org/10.1117/12.417514

KEYWORDS: Microwave radiation, Telecommunications, Fourier transforms, Buildings, Signal attenuation, Network architectures, Scattering, Mie scattering, Free space optical communications, Infrared radiation

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Proceedings Article | 27 January 1999 Paper

Multibeam-multipath terrestrial lasercom terminal

Heinz Willebrand

Proceedings Volume 3532, (1999) https://doi.org/10.1117/12.338977

KEYWORDS: Lenses, Connectors, Laser communications, Metals, Optical benches, Telecommunications, Optical fibers, Laser development, Prototyping, Networks

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Proceedings Article | 1 May 1996 Paper

Adaptive robust optical fiber receiver/transmitter

Heinz Willebrand, Jon Sauer

Proceedings Volume 2690, (1996) https://doi.org/10.1117/12.238932

KEYWORDS: Receivers, Wavelength division multiplexing, Transmitters, Data transmission, Electronics, Computer networks, Optical fibers, Sensors, Wavelength division multiplexing networks, Detector arrays

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Proceedings Article | 17 October 1994 Paper

Spatially and temporally resolved IR image detection with a semiconductor-gas-discharge device

S. Teperick, Yuri Astrov, Leonid Portsel, Heinz Willebrand, Thomas Gauselmann, Hans-Georg Purwins

Proceedings Volume 2269, (1994) https://doi.org/10.1117/12.188667

KEYWORDS: Semiconductors, Silicon, Visible radiation, CCD cameras, Electrodes, Cameras, Temperature metrology, Infrared technology, Zinc, Imaging systems

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Proceedings Article | 1 November 1993 Paper

Speed properties of a gas-discharge gap IR-visible converter studied with a streak-camera system

Leonid Portsel, Hans-Georg Purwins, Yuri Astrov, Heinz Willebrand

Proceedings Volume 2020, (1993) https://doi.org/10.1117/12.160573

KEYWORDS: Semiconductors, Electrodes, Silicon, Sensors, Streak cameras, Infrared technology, Photodetectors, Zinc, Image processing, Semiconductor lasers

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Showing 5 of 12 publications

Conference Committee Involvement (1)

Current Developments in Lens Design and Optical Engineering IV

3 August 2003 | San Diego, California, United States

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