Abdullah Al Amin

Dual-LP 11 mode 4x4 MIMO-OFDM transmission over a two-mode fiber

We report successful transmission of dual-LP(11) mode (LP(11a) and LP(11b)), dual polarization coherent optical orthogonal frequency-division multiplexing (CO-OFDM) signals over two-mode fibers (TMF) using all-fiber mode converters. Mode converters based on mechanically induced long-period grating with better than 20 dB extinction ratios are realized and used for interfacing single-mode fiber transmitter and receivers to the TMF. We demonstrate that by using 4×4 MIMO-OFDM processing, the random coupling of the two LP(11) spatial modes can be successfully tracked and equalized with a one-tap frequency-domain equalizer. We achieve successful transmission of 35.3 Gb/s over 26-km two-mode fiber with less than 3 dB penalty.

Transmission of 107-Gb/s mode and polarization multiplexed CO-OFDM signal over a two-mode fiber

In addition to the dimensions of time, frequency, complex constellation, and polarization, spatial mode can be the fifth dimension to be explored for modulation and multiplexing in optical fiber communications. In this paper, we demonstrate successful transmission of 107-Gb/s dual-mode and dual-polarization coherent optical orthogonal frequency-division multiplexing (CO-OFDM) over a 4.5-km two-mode fiber. A mechanically-induced LP01/LP11 mode converter is used as the mode selective element in a spatial-mode multiplexed system.

Highly Spectrally Efficient DWDM Transmission at 7.0 b/s/Hz Using 8

In this paper, we discuss the realization of wavelength-division multiplexing (WDM) transmission at high spectral efficiency. For this experiment, coherent polarization-division multiplexing--orthogonal frequency-division multiplexing (PDM-OFDM) is used as a modulation format. PDM-OFDM uses training symbols for channel estimation. This makes OFDM easily scalable to higher level modulation formats as channel estimation is realized with training symbols that are independent of the constellation size. Furthermore, because of its well-defined spectrum OFDM requires only a small guard band between WDM channels. The dependence of the number of OFDM subcarriers is investigated with respect to the interchannel linear crosstalk. At a constant data rate the number of OFDM subcarriers is estimated to achieve lower linear crosstalk in order to achieve higher spectral efficiency. We then experimentally demonstrate dense WDM (DWDM) transmission with 7.0-b/s/Hz net spectral efficiency using 8 × 65.1-Gb/s coherent PDM-OFDM signals with 8-GHz WDM channel spacing utilizing 32-quadrature-amplitude-modulation subcarrier modulation. Successful transmission is achieved over 240 km standard single-mode fiber (SSMF) spans with hybrid erbium-doped fiber amplifiers/Raman amplification.

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Spectral efficient transmission of 8×65.1-Gbit/s PDM-OFDM is reported over 240 km. Using coherent detection and 32-QAM subcarrier modulation the channel spacing is reduced to 8 GHz, allowing a net spectral efficiency of 7.0 bit/s/Hz.

65.1-Gb/s Coherent PDM-OFDM

An integrated semiconductor 1times5 InP-InGaAsP optical phased-array switch is fabricated and characterized. Using the carrier-induced refractive index change of InGaAsP waveguide, we achieve successful switching to five output ports with less than 60-mA current injection. Wide operating bandwidth covering the entire C-band (1520-1580 nm) and nanoseconds dynamic response are demonstrated, making it potentially applicable to large-capacity wavelength-multiplexed optical-packet-switching routers.

DWDM transmission with 7.0-bit/s/Hz spectral efficiency using 8×65.1-Gbit/s coherent PDM-OFDM signals

In this letter, we investigate 132.2-Gb/s polarization-division-multiplexed orthogonal frequency-division-multiplexing (PDM-OFDM) transmission at 25-GHz channel spacing. We show that the nonlinear tolerance is dependent on the OFDM symbol length. By using 14.4-ns-long OFDM symbols, 7 times 132.2-Gb/s transmission of PDM-OFDM at 4-b/s/Hz spectral efficiency is reported over 1300-km standard single-mode fiber.

InP–InGaAsP Integrated 1

Space-division multiplexing (SDM) based on few-mode fibers has been studied as a promising technique to increase fiber capacity. In this letter, we show optimal design and simulation of a low-loss fused fiber mode coupler, one of the most critical enabling components for SDM transmission systems. We first analyze the performance of a 3 × 1 fused fiber mode coupler with asymmetric waveguide structure by fusing a single-mode fiber and a two-mode fiber (TMF) together. A minimum loss of <; -1.9 dB and extinction ratio above 19 dB is predicated for both LP11 modes, over a wide wavelength range of 1505-1600 nm. We then analyze the performance of another fused fiber mode coupler with symmetric waveguide structure by fusing two TMFs together. A minimum loss of below 0.4/0.7 dB is predicated for both LP11 and LP01 modes.

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We report the first few-mode compatible optical add/drop multiplexer (OADM) that enables add/drop functionality for mode division multiplexed (MDM) superchannels. The OADM is comprised of two cascaded free-space thin-film filters with 5° incident angle. The transmission of MDM superchannel CO-OFDM signals via the OADM is investigated. The experimental result shows that the OSNR penalties for add, drop and through ports are 2.6, 2.4, 0.7 dB, respectively for 3x318 Gb/s superchannels.

5 Optical Switch Using Arrayed Phase Shifters

We demonstrate the use of mechanical grating based mode converters to achieve two forms of dual-spatial-mode transmission: LP₀₁ and LP₁₁, and dual LP₀₁ modes. High modal extinction ratio (>; 20 dB) is shown for the mode converter within a 10-nm wavelength range. We first present 107-Gb/s coherent optical OFDM (CO-OFDM) transmission over a 4.5-km two-mode fiber using LP₀₁ and LP₁₁ modes where the mode separation is performed optically. We then show 58.8-Gb/s CO-OFDM transmission using dual LP₁₁ modes where the mode separation is achieved via 4 × 4 electronic MIMO processing.

132.2-Gb/s PDM-8QAM-OFDM Transmission at 4-b/s/Hz Spectral Efficiency

8 times 66.8-Gbit/s DWDM transmission is demonstrated over 640-km SSMF with 9-GHz channel spacing. Employing coherent detected polarization-division-multiplexing OFDM with 16-QAM subcarrier modulation, a record spectral efficiency of 5.6 bit/s/Hz is achieved.