Tiffany Ko - Optical Rf Cancellation Poster

Optical interference cancellation of radio frequency signals Tiffany Ko, Maddie Lu, John Suarez, Paul Prucnal Department of Electrical Engineering, Princeton University

Introduction

Experimental Design & Setup Components

Military communications require the ability to detect weak radio frequency signals amidst more powerful signals. •

• Two lasers emitting at ~λ = 1550nm with a power of approximately 10.5 dBm • Two identical Mach-Zehnder interferometers • “True” time delay device • Optical attenuator • Erbium-doped fiber amplifier (EDFA)

Effective cancellation systems have been realized using electronic circuitry [2].

• With the advent of optical technologies, we aim to improve the performance of such cancellation systems [1]. • Specific advantages of using optical circuits include increased precision in identifying the small signal due to less system vulnerability to electrical noise, and the frequencyindependence of optical gain and delay.

Signal A

A+B

Signal B

Laser #1 optical attenuator Laser #2

Signal Analyzer

T

true‐time delay device Mach‐Zehnder optical interferometers

Figure 2: Experimental Setup Design

Mach-Zehnder interferometers

Our objective is to design a robust optical cancellation system which eliminates the detrimental effects of strong signal transmission in the presence of weak signal reception. Figure 1: Transmittance transfer curve of the  Mach‐Zehnder electro‐optic modulator

Results

• Introduce phase shifts by simply splitting a signal and altering its path length • Can be used in “counter-phase modulation,” where the signals are modulated in the linear regimes with both positive and negative slope [3] • Signal “A” is split and sent to the Mach-Zehnder interferometers

Conclusion

Signal Self-Cancellation

Small Signal Extraction

• Biasing the interferometers on quadrature points of the positive and negative slopes of the transmittance curve allows for Signal “A” to be effectively cancelled 1 0 13 dBm, minimum power at -62.39 62 39 dBm, • λ = 1550nm, peak power at 2 2.13 giving ~65 dB of cancellation

• A broadband Signal “A” (100 Mhz wide, centered at 3 Ghz) is combined with a small Signal “B”, initially buried along the noise level • Using counter-phase modulation, we can now extract Signal “B”

We have demonstrated RF filtering using optical signal processing by transferring the problem into the optical domain and utilizing its advantages distinct advantages. Additionally, current work is underway to more efficiently analyze signals through experimental automation using LabVIEW©. In the future, we hope to further investigate the extent of signal extraction with respect to signal-to-noise ratio, small signal to large signal ratio, and the consequences of various types of noise.

References R f • [1]: W. Chang, RF Photonic Technology in Optical Fiber Links, Cambridge University Press: 2002. • [2]: J. Cai, D. Upp, R. Dehmubed, H. Opper, G. Taylor, and J. Foshee, “Photonic Applications for Time Delay Interference Cancellation Systems,” SPIE Proceedings, Vol. 4998, 2003, pg 122-132 • [3]: J. Capmany, D. Pastor, B. Ortega, J. Mora, and M. Andrés, “Photonic processing of microwave signals,” IEE Optoelectronic Proceedings, Vol. 152 No. 6, December 2005, pg 299-320