Ho-Jin Song

Signal up-conversion by using a cross-phase-modulation in all-optical SOA-MZI wavelength converter

All-optical signal up-conversion into the millimeter-wave frequency band is demonstrated using a semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI) wavelength converter, which is based on a cross phase modulation (XPM) effect in the SOA. This scheme shows good conversion efficiency with polarization immunity and no increase in phase noise. The measured phase noise of the up-converted RF signal of 32.5 GHz is -79.2 dBc/Hz at 10 KHz offset, which is limited by that from the LO signal. A two-tone measurement is performed to characterize the linearity of the signal up-conversion. The measured spurious free dynamic range (SFDR) is 75.2 dB/spl middot/Hz/sup 2/3/, which meets the SFDR requirement for mobile communication systems.

Error-free simultaneous all-optical upconversion of WDM radio-over-fiber signals

A simultaneous all-optical upconversion technique for cost-effective wavelength-division-multiplexing (WDM) radio-over-fiber (RoF) applications utilizing a semiconductor optical amplifier (SOA) Mach-Zehnder interferometer is investigated. The proposed upconversion scheme uses only one frequency upconverter for multi-RoF channels, thereby reducing the complexity and cost of the system. Error-free simultaneous all-optical upconversion of two WDM intermediate frequency (IF) channels (155-Mb/s differential phase-shift keying signal at 2.5 GHz) to an optical radio frequency signal (22.5 GHz) is achieved. In addition, the effect of gain saturation of the SOA due to the increased number of WDM IF channels on bit-error-rates performance is also experimentally investigated.

An all-optical frequency up-converter utilizing four-wave mixing in a semiconductor optical amplifier for sub-carrier multiplexed radio-over-fiber applications.

A novel all-optical frequency up-converter utilizing four-wave mixing (FWM) in a semiconductor optical amplifier (SOA) was proposed and experimentally demonstrated. The frequency up-converter converted an optical intermediate frequency (IF) signal (f(IF) = 2.5 GHz) to an optical radio frequency (RF) signal (f(RF) = 35 and 40 GHz) through mixing with an optical local oscillator (LO) signal (f(LO) = 37.5 GHz). The up-converter showed positive conversion efficiency of 5.77 dB for the optical IF power of -22 dBm and the optical LO power of -13 dBm. This scheme showed broad bandwidths with respect to both LO and IF frequencies. The up-converter showed a phase noise of -84.5 dBc/Hz for the LO frequency of 37.5 GHz (f(LO)) and the offset frequency of 10 kHz after the frequency up-conversion.

All-optical Frequency Up-conversion Technique using Four-wave Mixing in Semiconductor Optical Amplifiers for Radio-over-fiber Applications

An all-optical frequency up-conversion technique based on a four-wave mixing (FWM) effect in semiconductor optical amplifiers (SOAs) was utilized for conversion of an optical intermediate frequency (IF) signal (2.5 GHz) to an optical radio frequency (RF) signal (40 GHz) by mixing with an optical local oscillator (LO) signal (37.5 GHz). This scheme provides positive conversion efficiency of 5.77 dB for the optical IF power of -22 dBm and the optical LO power of -13 dBm. The conversion efficiency was almost flat for the LO frequency range from 20 GHz to 47.5 GHz. The phase noise at the LO frequency of 37.5 GHz was -84.5 dBc/Hz (at 10 kHz offset) after the frequency up-conversion.

All-optical frequency down-conversion for full-duplex WDM RoF systems utilizing an SOA-MZI

An all-optical frequency down-conversion technique utilizing an SOA-MZI, which can be used for a full-duplex WDM RoF system with an all-optical frequency upconversion technique, is proposed and experimentally demonstrated. An optical RF signal at 22.5 GHz is harmonically down-converted to an optical IF signal at 2.5 GHz using a 10 GHz optical LO signal. For wavelengths of the RF signal between 1548 and 1558 nm, the conversion efficiency of the SOA-MZI down-converter for counter- and co-directional operations are approximately 1.5 ∼ 3 dB.

All-optical harmonic frequency up-conversion for a WDM radio over fiber system

All-optical harmonic frequency up-conversion into millimeter wave frequency over WDM radio over fiber application is demonstrated by using a semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI), which is based on cross phased modulation (XPM) effect in the SOA. Maximum frequency conversion efficiencies from f/sub IF/ to f/sub LO/ /spl plusmn/ f/sub IF/ and 2f/sub LO/ /spl plusmn/ f/sub IF/ are 13.2 dB and 3.1 dB, respectively. The efficiency of 2nd harmonic frequency up-conversion is positive for the IF signal wavelength between 1547.22 nm and 1560.61 nm. The phase noise of the up-converted signal at 2f/sub LO/ /spl plusmn/ f/sub IF/ is -80.0 DBc/Hz with 1 kHz offset frequency, which is limited by that of the LO source.

BER and SFDR Characteristics of an FWM-Based All-Optical Frequency Upconverter

We have experimentally investigated the bit-error-rate (BER) and spurious-free dynamic range (SFDR) characteristics of an all-optical frequency upconverter based on the four-wave-mixing effect in a semiconductor optical amplifier for radio-over-fiber networks. The generation and error-free transmission of an optical radio-frequency signal having 155.52-Mb/s differential phase-shift keying data at a carrier frequency of 26.5 GHz are achieved. The dynamic ranges of an optical intermediate frequency (IF) input signal estimated from the BER and SFDR measurements are approximately 12 and 16 dB, respectively. The SFDR of the upconverter is larger than 77 dBmiddotHz2/3 for the IF frequencies ranging from 1 to 12 GHz.

Linearity of all-optical frequency upconverter utilizing four-wave mixing for radio-over-fiber applications

The linearity performance of an all-optical frequency upconverter utilizing four-wave mixing (FWM) is investigated in a semiconductor optical amplifier (SOA). The upconversion method shows a good linearity which meets requirement for microcellular personal communication systems.

All-optical frequency up-converter utilizing a four-wave mixing effect in a semiconductor optical amplifier

An all-optical frequency up-converter utilizing a four-wave mixing effect in a semiconductor optical amplifier is experimentally demonstrated. In order to characterize a spurious free dynamic range, the third-order inter-modulation distortion signal power is measured by a two-tone test. The spurious free dynamic range of the photonic frequency up-converter is 81 dB-Hz2/3 for the optical LO power of -10 dBm and the optical IF power of -16 dBm. The scheme shows a positive conversion efficiency of 5.77 dB for the optical IF power of -22 dBm and the optical LO power of-13 dBm.

Simultaneous all-optical frequency upconversion for WDM radio over fiber applications

WDM radio over fiber (RoF) system utilizing a simultaneous all-optical frequency upconverter is proposed and experimentally demonstrated. The proposed scheme reduces the complexity and cost of the RoF system by using a single frequency upconverter for generation of optical RF signals having different wavelengths. Error free simultaneous harmonic frequency upconversion of two IF channels, which contain 155.52 Mbit/s differential-phase shift keying data at 2.5 GHz (fIF), to an optical RF signal having the RF frequency of 22.5 GHz (2fLO+fIF) using a LO frequency of 10 GHz (fLO) without performance degradation due to interchannel interference is achieved.