Extended Reach 10 Gb/s Transmission with an Optical I/Q Modulator Using VCSELs over OFDM-Based Multimode Fiber Link

Deepak Kedia,Monika Nehra

doi:10.1155/2018/2395495

Abstract

This paper investigates the possibilities of extending the reach of a 10 Gb/s orthogonal frequency division multiplexing- (OFDM-) based multimode fiber (MMF) link with an optical I/Q modulation technique through vertical cavity surface emitting lasers (VCSELs). The proposed I/Q modulation technique comprises two VCSELs in a 90° hybrid combination to produce I/Q modulated OFDM signal. The results show the excellent performance (in terms of BER and Q factor) of the direct-detection optical- (DDO-) OFDM system with the proposed I/Q modulation in comparison to the direct modulation case. The proposed system is able to achieve worst-case BER of about 1.8616 × 10−3 and Q factor of about 10.9949 dB over a 5 km MMF link. The I/Q modulation technique in the DDO-OFDM system has further been investigated for extending the transmission reach of the MMF link using multispan configuration.

Highlights

To date, the implementation of multimode fiber (MMF) links has gained significant attention for high-speed transmission over local area networks (LANs)
In MMF, the signal propagates on different fiber modes with different group velocities that result in differential modal delay (DMD)
The number of orthogonal frequency division multiplexing- (OFDM) subcarriers is set to 64, while inverse fast Fourier transform (IFFT) covers 256 samples and zero padding is set in the middle of the OFDM symbol

Summary

Introduction

The implementation of MMF links has gained significant attention for high-speed transmission over local area networks (LANs). An optical I/Q modulator using VCSELs is being proposed for 10 Gb/s data rate MMF link with a transmission reach of 5 km. The use of direct modulation laser is beneficial to improve the capabilities of the optical link in terms of distance-capacity product [12] Both VCSEL sources are operated at the same wavelength (1550 nm) and the outputs of both VCSELs are combined in a 90∘ hybrid to produce the I/Q modulated optical OFDM signal. The delay of interferometer is adjusted to one-symbol duration This intensity information can be detected by the photodiodes, where the resulting photocurrent shows the nonlinear mapping of baseband OFDM signal. The OFDM receiver performs the reverse operation to that of OFDM transmitter as (i) analogto-digital conversion (ADC), (ii) removal of CP, and (iii) fast Fourier transform (FFT) to convert the OFDM symbols back into data bits [16]

Simulation Results

Conclusion

10 EG MMF