KEYWORDS: Radio over Fiber, Signal to noise ratio, Radio optics, Transmitters, Receivers, Quadrature amplitude modulation, Telecommunications, Modulators, Optical amplifiers, Optical engineering
An optical transmitter system-on-packaging (TxSoP) with an electro-absorption modulator (EAM) was developed for 60-GHz band rf with radio-over-fiber (rf/RoF) uplink. An analysis to develop the TxSoP with a small noise figure was performed so that the noise figure of the modified TxSoP decreased by 15 dB. The rf/RoF uplink with the modified TxSoP was established, and the error vector magnitude (EVM) and the signal-to-noise ratio (SNR) of the link were measured between 2.2% and 3.2% and between 26 dB and 29 dB from 140 MHz to 800 MHz, respectively. Digital CATV signals corresponding to 86 channels were transmitted through the link, and total throughput of the link was 2.6 Gbps.
KEYWORDS: Transmitters, Radio over Fiber, Optical amplifiers, Signal to noise ratio, Analog electronics, Radio optics, Modulators, Photodetectors, Quadrature amplitude modulation, Optical engineering
We developed an analog optical transmitter module with rf gain for 60 GHz radio-over-fiber (RoF) application narrow band. It consists of an electroabsorption modulator (EAM), a filter, and amplifier. The frequency response increased about 20 dB from the noise level around 60 GHz with the EAM bias voltage of −1.6 V. The 3 dB bandwidth was about 2.2 GHz. The signal-to-noise ratio of the RoF link with transmitter module was measured and the noise figure was obtained, which were compared with those of narrow band EAM module with an additional amplifier. A 16 quadrature-amplitude-modulation data signal could be transmitted with the signal-to-noise ratio of 15.9 dB. The noise figure of the RoF link with the transmitter module was calculated 19.2 dB, which is about 7.5 dB larger than that of the EAM module with rf amplifier at the bias voltage −2.0 V.
We proposed the vertical mode coupling structure (VMCS) for monolithic integration of optoelectronic devices. The electroabsorption duplexer (EAD) chip was fabricated by monolithically integrating both a waveguide photodiode (PD) and an electroabsorption modulator (EAM) in association with traveling wave electrodes. Using an EAD we presented a transceiver (TRx) module for dual functions of both electrical-to-optical (E/O) and optical-to-electrical (O/E) conversions at 60GHz band. The responsivity and the extinction ration of the EAD were 0.72 A/W and 20 dB at -4 Vdc, respectively. The coupling loss between the optical fiber and the device facet was as small as 1.96 dB. The small signal 3 dB bandwidth of E/O and O/E response was 25 GHz and 8 GHz, respectively. We also investigated the issues of RF packaging in which the optoelectronic and electronic amplifier devices were co-packaged in a single housing.
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