We demonstrate the first experimental implementation of an optical Fast-OFDM (FOFDM) system with a reduced sub-carrier spacing equal to half of the symbol rate. The performance was evaluated in terms of BER for 7.174Gbit/s and 14.348Gbit/s BPSK-FOFDM signals. IntroductionOrthogonal frequency division multiplexing (OFDM) is a promising modulation format that has attracted a lot of interest recently due to its increased spectral efficiency and better tolerance to transmission impairments such as chromatic dispersion (CD) [1][2]. OFDM has a sub-carrier spacing equal to the symbol rate per sub-carrier which satisfies the othogonality condition [1] and requires a matched filter at the receiver to receive the data crosstalk-free.However, if the phase differences between the sub-carriers are controlled, the minimum frequency spacing for crosstalk-free operation can be reduced to half of the symbol rate per sub-carrier. This technique has been theoretically proposed for wireless applications and is known as fast OFDM [3]. Recently this technique has been theoretically proposed for use in optical communications as optical fast OFDM (FOFDM) [4][5]. This scheme achieves the Nyquist rate, but in contrast to conventional OFDM, it uses half the sub-carrier spacing and only single-quadrature modulation formats. The sub-carrier multiplexing/demultiplexing in optical FOFDM can be implemented by a discretecosine transform (DCT) [4] or the recently proposed discrete-Fourier transform (DFT) [5].Since only single-quadrature modulation is used for FOFDM the phase estimation in the coherent detection at the receiver is simplified. FOFDM also reduces the transmitter complexity when compared to a conventional OFDM system having the same spectral efficiency and total data rate [3][4][5].To our knowledge FOFDM has not previously been demonstrated experimentally in any wireless or optical communication system.In this paper, we experimentally demonstrate the world first binary phase shift keying (BPSK)-based double-side-band (DSB) optical FOFDM system. Two configurations are reported with net bit rates of 7.174Gbit/s and 14.348Gbit/s. This result also represents the first experimental demonstration of any FOFDM system reported to date. The performance of the optical FOFDM system was evaluated by measuring the bit error

Abstract-We show the potential use of a single photodetector for multichannel pulse monitoring. Two-photon absorption in a microcavity structure is used as the nonlinear optical technique for pulse monitoring. Angle tuning of the device allows the resonance to be tuned. For the device studied here that is optimized for 2-ps pulses, a possible tuning range of 55 nm is shown.

Abstract-Due to the introduction of new broadband services, individual line data rates are expected to exceed 100 Gb/s in the near future. To operate at these high speeds, new optical signal processing techniques will have to be developed. This paper will demonstrate that two-photon absorption in a specially designed semiconductor microcavity is an ideal candidate for optical signal processing applications such as autocorrelation, sampling, and demultiplexing in high-speed wavelength-divisionmultiplexed (WDM) and hybrid WDM/optical time-divisionmultiplexed networks.

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For optical pulse incidence as compared with continuous-wave incidence, the enhancement of two-photon absorption inside a high-finesse planar microcavity is reduced, the pulse inside the cavity and the cavity spectrum are broadened. The analysis shows that for transform-limited pulse incidence, the true pulsewidth and the cavity frequency resolution can be estimated if the cavity lifetime or the cavity bandwidth has been obtained from the reflection or transmission spectrum of the cavity.