Kazuki Tanaka

Long-Reach Coherent WDM PON Employing Self-Polarization-Stabilization Technique

We propose a simple self-polarization-stabilization technique for the wavelength-division-multiplexed passive optical network implemented with reflective semiconductor optical amplifiers (RSOAs) and self-homodyne coherent receivers. By placing a 45° Faraday rotator in front of the RSOA in the optical network unit, the state-of-polarization of the upstream signal becomes orthogonal to that of the linearly polarized seed light at the input of the coherent receiver regardless of the birefringence in the transmission link. Thus, we can achieve the polarization stability of the upstream signal at the input of the coherent receiver. We first implement a self-homodyne receiver by using the proposed self-polarization-stabilization technique and measure its sensitivity by using 2.5-Gb/s binary phase-shift keying signals in the laboratory. The result shows an excellent receiver sensitivity of -46.4 dBm. We also confirm the efficacy of the proposed technique in the transmission experiment over 68-km long link partially composed of installed (buried and aerial) fibers. No significant degradation in the receiver sensitivity is observed during the 10-h experiment despite the large polarization fluctuations occurred in these installed fibers.

Self-polarization-stabilization technique for long-reach coherent WDM PON

We demonstrate a simple self-polarization-stabilization technique for the long-reach RSOA-based WDM PON implemented with self-homodyne receivers. The effectiveness of this technique is confirmed in 2.5-Gb/s transmission experiments over 68-km long link partially composed of installed fibers.

40 Gbit/s single-channel soliton transmission over 10200 km without active inline transmission control

By reducing the timing jitter and soliton-soliton interaction effectively, 40 Gbit/s transmission over 10200 km has been successfully demonstrated for the first time without any active components in the transmission line.

25-Gb/s TDM Optical Link Using EMLs for Mobile Fronthaul Network of LTE-A System

We propose and demonstrate a common public radio interface (CPRI)-compliant 25.2923-Gb/s mobile fronthaul network for long term evolution-advanced (LTE-A) systems. In order to meet the CPRI specifications and the stringent latency requirement of the LTE-A fronthaul network cost-effectively, we use the synchronous time-division-multiplexing, forward-error correction, and electrical equalization techniques. To enhance the cost-effectiveness, we also use an electroabsorption-modulated laser and exploit the possibility of using simple modulation formats such as the ON-OFF keying, electrical duobinary, and four-level pulse amplitude modulation. The performance of the proposed network is evaluated experimentally in terms of the tolerances to fiber dispersion and optical reflection.

400 Gbit/s (20/spl times/20 Gbit/s) dense WDM transmission using soliton-based RZ signals

400 Gbit/s (20/spl times/20 Gbit/s) soliton-based RZ signals were successfully transmitted over 2000 km with a channel spacing of 0.8 nm by using pre- and periodical dispersion compensation scheme. We investigated the possibility to reduce the channel spacing to less than 1 nm in 20 Gbit/s-based soliton WDM systems and demonstrated 400 Gbit/s (20/spl times/20 Gbit/s) transmission over 2000 km with a channel spacing of 0.8 nm using dispersion flattened fiber with pre- and periodic dispersion compensation.

Broadband IF-Over-Fiber Transmission With Parallel IM/PM Transmitter Overcoming Dispersion-Induced RF Power Fading for High-Capacity Mobile Fronthaul Links

We demonstrate a broadband and long-distance intermediate frequency-over-fiber (IFoF) transmission scheme employing a transmitter composed of parallel intensity/phase (IM/PM) modulators with appropriate bandwidth allocations to IM and PM. Due to the proposed scheme, we can eliminate all the null frequencies caused by dispersion-induced RF power fading, which, in turn, enables us to significantly increase the available bandwidth. In addition, our system does not require any synchronization between IM and PM, which reduces complexity compared to conventional parallel transmitter architecture. We successfully transmitted 20

Optical and wireless integrated technologies for mobile networks towards beyond 5G era

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Novel scheme of PTP packets distribution over TDM-PON for time synchronization among mobile base stations

360 MHz filtered orthogonal-frequency-division-multiplexed signals corresponding to a common public radio interface equivalent data rate of 524.28 Gbps over a 30- and 40-km single-mode fiber satisfying the 8% threshold for the error-vector magnitude values for all the subcarriers. These results show that our proposed IFoF transmission scheme is scalable to long-distance mobile fronthaul links for 5G and beyond.

Optical and wireless integrated technologies for future mobile networks

The peak rate of coming 5 G mobile services will be comparable to that of FTTH. In this paper, we will discuss integrated optical and wireless technologies, such as RoF, for efficient use of bandwidth of future mobile back/front-haul networks towards beyond 5G era.

Reflection tolerance enhancement of optical video distribution systems by using laser current dithering

We propose a precise time synchronization technique for mobile base stations by a novel PTP packets distribution scheme over TDM-PON and experimentally demonstrate the effectiveness achieving the time accuracy within 13 ns for 72 hours.