IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 24, NO. 10, MAY 15, 2012 851 10-Gb/s Pulse-Amplitude Modulated Transmission Over 1-mm Large-Core Polymer Optical Fiber Sven Loquai, Roman Kruglov, Christian-Alexander Bunge, Member, IEEE, Olaf Ziemann, and Bernhard Schmauss, Member, IEEE Abstract— The authors report on a 10-Gb/s transmission over 1-mm large-core diameter polymer optical fiber (POF) using pulse-amplitude modulation. For the first time, a real-time 10-Gb/s eye-diagram is shown after 5-m standard step-index POF (SI-POF), even with an eye-safe transmitter (0 dBm). With an offline decision feedback equalization technique, a link length of 10-m SI-POF, respectively, 25-m GI-POF was achieved. With a slightly higher optical power of +5 dBm, the maximum link length could even be increased to 30-m SI-POF and 60-m GI-POF. Index Terms— Eye-safe, optical communication, polymer optical fiber, pulse-amplitude modulation. I. I NTRODUCTION P OLYMER optical fiber (POF) is a promising transmission media for broadband in-home networks but also for inter- connection and short-reach connections up to 100 m, where low complexity transceivers and low latency are important issues. With advanced modulation techniques like discrete multi- tone modulation (DMT), the potential of large-core 1 mm POF to transmit 10 Gb/s was already demonstrated [1-3]. But while this DMT modulation format makes good use of the available bandwidth, it requires considerable signal processing at the transmitter and receiver. It also adds latency to the transmission due to the block-wise nature of the DMT modulation format. In the given letter we demonstrate for the first time pulse- amplitude modulation (PAM-4) of 10 Gb/s over 1 mm large- core POF using a newly developed optical POF receiver com- prising a large area photodetector (PD) with a transimpedance amplifier (TIA). Manuscript received January 9, 2012; revised February 16, 2012; accepted February 19, 2012. Date of publication February 27, 2012; date of current version April 18, 2012. This work was supported in part by the Federal Ministry of Education and Research (BMBF) under Project 17016X10. S. Loquai, R. Kruglov, and O. Ziemann are with the Polymer Optical Fiber Application Center (POF-AC), University of Applied Sciences Nuremberg, Nuremberg 90489, Germany (e-mail: sven.loquai@pofac.ohm-hochschule.de; roman.kruglov@pofac.ohm-hochschule.de; olaf.ziemann@pofac.ohm- hochschule.de). C.-A. Bunge is with the Hochschule f. Telekommunikation, Deutsche Telekom AG, Leipzig 04277, Germany (e-mail: bunge@hft leipzig.de). B. Schmauss is with the University of Erlangen-Nuremberg, Erlangen 91058, Germany (e-mail: bernhard.schmauss@lhft.de). Color versions of one or more of the figures in this letter are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/LPT.2012.2189002 Fig. 1. Schematic transmission setup used for the experiments. With this modulation format both issues of DMT transmission can be addressed. In contrast to DMT a much lower complexity is needed to modulate and demodulate the signal which results in a lower latency, lower power consump- tion and lower cost. Therefore PAM is a promising candidate for next-generation, low-latency 10 Gb/s transmission over large core 1 mm polymethylmetacrylate (PMMA) POF. II. TRANSMISSION SETUP The transmission setup is shown in Fig. 1. The edge- emitting laser diode (LD) or the Vertical-Cavity Surface- Emitting Laser (VCSEL) is directly driven with a pseudo random bit sequence mapped to a PAM-4 signal. The PAM-4 signal is generated by an arbitrary waveform generator (AWG) with a resolution of 10 bit and a sampling rate of 10 GSa/s. The transmitters used in the experiment are a commercially available edge-emitting laser diode with a wavelength of 650 nm and an optical output power of 7 mW, respectively, a VCSEL (Firecomms) with a wavelength of 660 nm and an optical output power of 1 mW which corresponds to eye-safe operation. The LD and the VCSEL are driven in their linear region with a modulation index of approximately m ≈ 0.8. The new developed POF receiver has an active diameter of ∅300 μm. A dielectric taper was used to increase the coupling efficiency between the POF and the photodiode. The real time oscilloscope captures the analog electrical signal with a resolution of 8 bits. For the offline processing 1041–1135/$31.00 © 2012 IEEE