Wireless access systems are attractive because of their potential high data rate transmissions. For example, frequency bands in the range from 3.1 GHz up to 10.6 GHz are allocated to Ultra Wide Band IEEE 802.15.3a standards for future Wireless Personal Access Networks (WPAN).
The frequency conversion of wireless signals in the optical domain is interesting since it benefits from the huge optical bandwidth for generation and distribution of up-converted sub-bands.
This papers explores different techniques for photonics generation of microwave mixing with digital modulation of the microwave sub-carriers, at 1550 nm. The solutions exploit the non-linearity of different devices such as laser diodes, electro-optic modulators, dispersive fiber generating frequency-to-intensity modulation conversion. Comparisons are made regarding their potential applications to low-cost and broadband radio-over fiber systems like Ultra Wide Band over fiber. The mixing conversion gain, available bandwidth, complexity of the system, its applicability to broadband radio over fiber networks, are elements of comparison that are discussed in this paper.
An unbalanced Mach Zehnder interferometer (UMZ) is used here for up-conversion of a microwave subcarrier, with IQ modulation at 30 and 200 Msymb/s. Both QPSK and QAM-16 are investigated, and a low BER of 10-9 is demonstrated after detection of the up-converted microwave subcarrier for an optical power of -1dBm delivered by a directly modulated laser diode.
In this paper we show that integrated optics offer a very simple and low cost way to combine up to eight beams of an interferometric optical array. These beam combiners will allow accurate visibilities and phase closure terms measurements, and provide consequently, high quality information for astronomical image reconstruction. We present optical designs for two different chips. Using previous laboratory experiments we extrapolate the performances, constraints and limits of different beam combination concepts. In particular spatial encoding and temporal encoding of `all-in-one' schemes are compared and their main properties are evaluated.
We present a new technique for remote upconversion by inserting a passive all-optical device in the microwave (MW) fiber-optic link. Using a semiconductor laser directly modulated by two MW signals and an unbalanced Mach-Zehnder interferometer (UMZ) to convert optical frequency modulation into intensity modulation, mixing is achieved after photodetection. Experiments with a UMZ integrated on glass- substrate have demonstrated the feasibility of this optical method for MW mixing with a low cost device of easy fabrication. Temperature control of the device allows optimized mixing performance and stable response. This method permits to overcome the effect of chromatic dispersion in standard singlemode fiber systems operating in the 1.55 micrometers wavelength window. Due to the presence of high-frequency fundamental components in the optical field, the received power is considerably degraded during transmission and direct detection in conventional systems, using either direct or external modulation in the MW band. With the proposed technique, lower frequency components of the field can be transmitted. The insertion of the simple UMZ generates high frequency only at detection side, therefore the available fiber length is extended. As it is shown by simulation results, this method can be used for the upconversion of MW subcarriers carrying digital signals.
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