Ui Hyun Hong

Long-reach 10-Gb/s RSOA-based WDM PON employing QPSK signal and coherent receiver.

We demonstrate a long-reach wavelength-division-multiplexed passive optical network (WDM PON) operating at the symmetric rate of 10.3 Gb/s. For the cost-effectiveness, we realize the upstream transmission by utilizing directly-modulated TO-can packaged reflective semiconductor optical amplifiers (RSOAs) and digital coherent receivers. In addition, to overcome the limited modulation bandwidth of this TO-can packaged RSOA (~2.2 GHz) and operate it at 10.3 Gb/s, we utilize the quadrature phase shift keying (QPSK) format and the electronic phase equalization technique. The result shows that we can extend the maximum reach of the 10.3-Gb/s RSOA-based WDM PON to ~80 km without using any remote amplifiers.

103-Gb/s Long-Reach WDM PON Implemented by Using Directly Modulated RSOAs

We propose and demonstrate a long-reach wavelength-division-multiplexed passive optical network (WDM PON) capable of providing 100-Gb/s service to each subscriber, for the first time to the best of our knowledge. For cost-effectiveness, this network is implemented in loopback configuration by using directly modulated reflective semiconductor optical amplifiers (RSOAs) at 25.78 Gb/s. For the modulation of the RSOA at such a high-speed, we have to minimize the electrical parasitics by using the butterfly package. Also, to overcome the limited bandwidth of the RSOA, we utilize the electronic equalization technique at the receiver. We use four RSOAs at each optical network unit for the 103-Gb/s upstream transmission. The operating wavelengths of these RSOAs are separated by the free-spectral range of the cyclic arrayed waveguide gratings used at the central office and remote node (RN) for (de)multiplexing the WDM channels. We extend the maximum reach of this WDM PON to be >; 120 km by using Erbium-doped fiber amplifiers at the RN. The results show that the error-free transmission can be achieved for all WDM channels in the wavelength range of >; 35 nm with sufficient power margins.

Maximum reach of long-reach RSOA-based WDM PON employing remote EDFA

We investigate the effects of the gain and position of the remote EDFA in a long-reach RSOA-based WDM PON. Using this result, we also estimate the maximum transmission reach limited by Rayleigh backscattering.

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.

10-Gb/s, 80-km reach RSOA-based WDM PON employing QPSK signal and self-homodyne receiver

We demonstrate 10-Gb/s, 80-km-reach RSOA-based WDM PON by utilizing the digital coherent detection and electronic phase equalization techniques. The upstream signal is obtained by directly modulating a TO-can packaged RSOA with 10-Gb/s QPSK signal.

Transmission of 40-Gb/s QPSK upstream signal in RSOA-based coherent WDM PON using offset PDM technique

We demonstrate the 40-Gb/s upstream transmission in the 60-km reach wavelength-division-multiplexed passive optical network (WDM PON) implemented by using directly modulated reflective semiconductor optical amplifiers (RSOAs) and self-homodyne receivers. It is difficult to operate the RSOA at 40 Gb/s due to its limited modulation bandwidth. To overcome this problem and generate 40-Gb/s upstream signal, we utilize the quadrature phase-shift-keying (QPSK) format and the offset polarization-division-multiplexing (PDM) technique. For this purpose, we install two RSOAs at each ONU and provide the seed light for these RSOAs by polarization-multiplexing the outputs of two lasers with a small frequency offset (20 GHz). This frequency offset is used to separate the polarization-multiplexed seed light by using a simple delay-line interferometer (DLI), instead of the polarization-beam splitter and polarization controller, at the ONU. The separated seed light is modulated by each RSOA at 20 Gb/s in the QPSK format, and then combined again by the DLI before sent back to the central office (CO). The results show that this WDM PON can support the transmission of 40-Gb/s channels spaced at 50 GHz over 60 km without using any remote optical amplifiers.

A simple carrier-phase estimator for high-speed RSOA-based coherent WDM PON

It has been recently reported that reflective semiconductor optical amplifiers (RSOAs) can be used as phase modulators for the cost-effective implementation of the high-speed wavelength-division-multiplexed passive optical networks (WDM PONs). For the detection of the phase-shift-keying (PSK) signal generated by using an RSOA, we should be able to estimate its carrier phase accurately at the digital coherent receiver. However, when the baud rate of this PSK signal is set to be much higher than the RSOAs modulation bandwidth, the conventional M-th power algorithm cannot estimate its carrier phase accurately. To solve this problem, we develop a simple carrier-phase estimation technique for the high-speed (>10 Gb/s) PSK signals generated by using bandwidth-limited RSOAs. This technique estimates the carrier phase of the PSK signal by measuring the angular direction of the opening occurred in the trajectory of the phasor diagram. By using the proposed technique, we demonstrate the upstream transmission of the 25.78-Gb/s quadrature phase-shift-keying (QPSK) signal generated by using an RSOA (3-dB bandwidth: 3.2 GHz) in a 60-km reach coherent WDM PON.

A simple carrier-phase estimation technique for high-speed RSOA-based coherent WDM PON

We propose a simple carrier phase estimation technique for the phase-modulated signal generated by using bandwidth-limited RSOA. By using this technique, we demonstrate 25.78-Gb/s QPSK upstream transmission in 60-km reach coherent RSOA-based WDM PON.

Demonstration of 40-Gb/s QPSK upstream transmission in long-reach RSOA-based coherent WDM PON using offset PDM technique

We demonstrate the 40-Gb/s QPSK upstream transmission in 60-km reach WDM PON (channel spacing: 50 GHz) implemented by using directly modulated RSOAs and self-homodyne receivers together with the offset PDM technique.

Multi-ring architecture for survivable WDM PON

We propose and demonstrate a multi-ring architecture for the survivable WDM PON. This architecture has an excellent scalability and the protection can be achieved by using a small amount of additional protection fibers.