Swen Koenig

Error Vector Magnitude as a Performance Measure for Advanced Modulation Formats

We examine the relation between optical signal-to-noise ratio (OSNR), error vector magnitude (EVM), and bit-error ratio (BER). Theoretical results and numerical simulations are compared to measured values of OSNR, EVM, and BER. We conclude that the EVM is an appropriate metric for optical channels limited by additive white Gaussian noise. Results are supported by experiments with six modulation formats at symbol rates of 20 and 25 GBd generated by a software-defined transmitter.

100 Gbit/s wireless link with mm-wave photonics

We demonstrate a single-input single-output photonic wireless link at 237.5 GHz with record 100 Gbit/s data transmission over 20 m. We use an optical heterodyne I/Q transmitter and a state-of-the-art active I/Q-MMIC at the receiver.

Quality metrics for optical signals: Eye diagram, Q-factor, OSNR, EVM and BER

Measuring the quality of optical signals is one of the most important tasks in optical communications. A variety of metrics are available, namely the general shape of the eye diagram, the optical signal-to-noise power ratio (OSNR), the Q-factor as a measure of the eye opening, the error vector magnitude (EVM) that is especially suited for quadrature amplitude modulation (QAM) formats, and the bit error ratio (BER). While the BER is the most conclusive quality determinant, it is sometimes difficult to quantify, especially for simulations and off-line processing. We compare various metrics analytically, by simulation, and through experiments. We further discuss BER estimates derived from OSNR, Q-factor and EVM data and compare them to measurements employing six modulation formats at symbol rates of 20 GBd and 25 GBd, which were generated by a software-defined transmitter. We conclude that for optical channels with additive Gaussian noise the EVM metric is a reliable quality measure. For nondata-aided reception, BER below 0.01 can be estimated from measured EVM.

Silicon-Organic Hybrid MZI Modulator Generating OOK, BPSK and 8-ASK Signals for Up to 84 Gbit/s

We report on high-speed multilevel signal generation and arbitrary pulse shaping with silicon-organic hybrid (SOH) Mach-Zehnder interferometer (MZI) modulators. Pure phase modulation exploiting the linear electrooptic effect allows the generation of multiple modulations formats at highest speed such as 40-Gbit/s on-off-keying (OOK) and binary-phase-shift keying (BPSK) and 28-Gbd 4-ASK and 8-ASK with data rates up to 84 Gbit/s. Additionally, beside NRZ pulse shaping, for the first time, Nyquist pulse shaping with silicon modulators is demonstrated to enable multiplexing at highest spectral efficiency.

Transmission of an 8-PSK modulated 30 Gbit/s signal using an MMIC-based 240 GHz wireless link

The transmission of complex modulated data signals with data rates up to 30 Gbit/s is successfully realized using a 240 GHz wireless link based on active MMIC components. The paper presents the transmission of QPSK and 8-PSK modulated signals over a distance of 40 m as well as a characterization of the RF frontend based on S-parameter measurements and back-to-back signal transmission. The link quality is evaluated in terms of error vector magnitude (EVM) measurement. For a symbol rate of 10 GBd, the EVM measurement shows values of 10.3% and 15.2% for the QPSK and 8-PSK signal, respectively.

Linear semiconductor optical amplifiers for amplification of advanced modulation formats

The capability of semiconductor optical amplifiers (SOA) to amplify advanced optical modulation format signals is investigated. The input power dynamic range is studied and especially the impact of the SOA alpha factor is addressed. Our results show that the advantage of a lower alpha-factor SOA decreases for higher-order modulation formats. Experiments at 20 GBd BPSK, QPSK and 16QAM with two SOAs with different alpha factors are performed. Simulations for various modulation formats support the experimental findings.

Corrections to “Error Vector Magnitude as a Performance Measure for Advanced Modulation Formats” [Jan 1, 2012 61-63]

In the above titled paper (ibid., vol. 24, no. 1, pp. 61-63, Jan. 1, 2012), equation (4) contains an error. The corrected equation is presented here. Additionally, the paper should include an Appendix, which is presented here.

20 Gbit/s wireless bridge at 220 GHz connecting two fiber-optic links

The feasibility of a wireless link at 220 GHz based on electronic upconversion and downconversion is demonstrated, connecting two optical links at data rates of up to 20 Gbit/s. We use either non-return-to-zero on-off keying with data rates up to 20 Gbit/s or electrical orthogonal frequency division multiplexing with data rates up to 9 Gbit/s. The wireless bridge connects the gateways of two spatially separated fiber sections, each with a length of up to 20 km.

Amplification of advanced modulation formats with a semiconductor optical amplifier cascade.

The convergence of optical metro networks and access networks extends the area of network coverage, and therefore requires the use of optical amplifiers. For this purpose, semiconductor optical amplifiers (SOA) would be attractive, because they are broadband, can be centered between 1250 nm and 1600 nm, and because they are cheap in production and operation. We show that signals encoded with advanced modulation formats such as BPSK, QPSK, 8PSK, and 16QAM can be amplified by a cascade of at least four SOAs. This enables high-capacity paths with a capacity in the order of Tbit/s for converged metro-access networks.

High-speed wireless bridge at 220 GHz connecting two fiber-optic links each spanning up to 20 km

Record-speed wireless data bridging at 220 GHz is demonstrated with a 20 Gbit/s NRZ-OOK and a 9 Gbit/s OFDM signal. We connect the wireless gateways of two fiber spans, each with up to 20 km.