Hideaki Tamai

Experimental study on time-spread/wavelength-hop optical code division multiplexing with group delay compensating en/decoder

10-Gb/s time-spread/wavelength-hop optical code generation and decoding were performed by group delay compensating fiber Bragg grating (FBG) en/decoder pair. A 10-km single-mode fiber (SMF) transmission of 10-Gb/s optical code division multiplexing (OCDM) was experimentally demonstrated.

First Demonstration of Coexistence of Standard Gigabit TDM-PON and Code Division Multiplexed PON Architectures Toward Next Generation Access Network

World-first coexistence trial of TDM and CDM giga-bit passive optical networks (PONs) was successfully completed. A very shallow minimum isolation of 7 dB between G- and CDM-PON at OLT and ONU in the ITU-T G.984.5 enhancement band was demonstrated. The feasibility of bidirectional transmission on the same wavelength was confirmed. The backscattering optical noise does not seriously affect the maximum reach of CDM-PON. Adding the CDM-PON onto GPON can provide following technical and economical impacts: low-cost coexistence, minimum service outage, and combination of best-effort and guaranteed-bandwidth for efficient and high-quality network services due to CDM feature.

First system demonstration of hitless λ-tuning sequence for dynamic wavelength allocation in WDM/TDM-PON

We propose hitless wavelength-tuning sequence for dynamic wavelength allocation in WDM/TDM-PONs and demonstrate highly frequent wavelength-tunings in 100-ms intervals without data-frame loss using MAC boards. Pay-as-you-grow operation based on the proposed sequence is also shown.

42dB Loss Budget Hybrid DWDM-CDM-PON without Optical Amplifier

First time, an unprecedented 42 dB loss budget was realized by using hybrid DWDM-CDM (code division multiplexing)-PON without optical amplifier. We experimentally demonstrated 100 km 16lambda-DWDM-CDM-PON bidirectional transmission with 62.5 Mbps times 32 users/lambda symmetry guaranteed bandwidth. Long reach PON is expected to reduce CapEx and OpEx cost.

Demonstration of Load-Balancing Operation Based on Hitless Dynamic Wavelength Allocation on Symmetric 40-Gbit/s λ-Tunable WDM/TDM-PON

This paper reports the world-first system-level demonstration of dynamic wavelength allocation (DWA) on a wavelength-tunable (λ-tunable) wavelength division multiplexing/time division multiplexing-passive optical network (WDM/TDM-PON). To achieve DWA, a DWA calculation is necessary that determines new optical network unit assignments to the optical line terminal ports according to the bandwidth demand. In addition, a wavelength-tuning (λ-tuning) sequence that induces no data-frame loss, i.e., a hitless λ-tuning sequence, is essential. First, we propose a bidirectional hitless λ-tuning sequence and investigate its feasibility using media access control boards that we developed for symmetric 40-Gbit/s λ-tunable WDM/TDM-PONs, which are also the worlds first. Then, with a DWA calculation according to the downstream traffic loads, we show automatic dynamic load-balancing operation.

Demonstration of 10 Gbit/s-Based Time-Spreading and Wavelength-Hopping Optical-Code-Division-Multiplexing Using Fiber-Bragg-Grating En/Decoder

We studied 10Gbit/s-based time-spreading and wavelength-hopping (TS-WH) optical code division multiplexing (OCDM) using fiber Bragg gratings (FBGs). To apply it to such the high bit rate system more than ten gigabit, two techniques are adopted. One is encoding with the maximum spreading time of 400 ps, which is four times as data bit duration, to encode without shortening chip duration. Another is encoder design. The apodized refractive index profile to the unit-gratings composing the encoder is designed to encode the pulses with 10-20ps width at 10Gbit/s rate. Using these techniques, 2 × 10Gbit/s OCDM is demonstrated successfully. In this scheme, transmission distance is limited due to dispersion effect because the signal has wide bandwidth to assign a wavelength-hopping pattern. We use no additional devices to compensate the dispersion, in order to construct simple and cost-effective system. Novel FBG encoder is designed to incorporate both encoding and compensating of group delay among chip pulses within one device. We confirm the extension of transmission distance in the TS-WH OCDM from the demonstration over 40 km-long single mode fiber.

Demonstration of 1.25 Gb/s

In this letter, 1.25 Gb/s × 8-channels simultaneous multiplexing using 8-chip electrical codes is experimentally demonstrated for the downlink of a 10-Gb/s electrically code-division-multiplexing passive optical network (ECDM-PON) system. For electrical encoding and decoding, 10-Gb/s multilevel signal generation and 10 Gchip/s correlator as a decoder are utilized. We demonstrate 10-Gb/s ECDM error-free optical transmission over 20 km of single-mode fiber.

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This paper presents the worlds first field trial of a 40-km reach and over 512-split symmetric-rate 40-Gbit/s λ-tunable time and wavelength division multiplexing passive optical network (TWDM-PON) that utilizes our newly developed high-speed λ-tunable optical network unit transceivers and automatic gain controlled semiconductor optical amplifier-based PON extender for repeater and central office use. The upstream signals for C-band and downstream signals for L+-band in our developed λ-tunable TWDM-PON comply with the wavelength plan of ITU-T G.989 series. In a field trial, we successfully demonstrate error free λ-tunable transmission for the 40-km reach and 1024-split (maximum number) symmetric-rate 40-Gbit/s λ-tunable TWDM-PON over installed standard single-mode fiber links, and advanced network functions such as dynamic load balancing, incremental system upgrade, optical subscriber unit protection, and OLT equipment power saving are also confirmed.

8-Channels ECDM Using Eight-Chip Electrical Coding

We proposed and demonstrated 40Gbps, 256-label optical packet switching employing a clockless serial optical code label processing. Eight different SSFBGs label recognizers with high auto- to cross-correlation peak ratio were used for optical label correlation.

Field Trial of Long-Reach and High-Splitting λ-Tunable TWDM-PON

This paper clarifies the scalability of the hitless wavelength-tuning (λ-tuning) sequence for dynamic wavelength allocation (DWA) on a λ-tunable wavelength-division-multiplexing/time-division-multiplexing passive optical network (WDM/TDM-PON). The λ-tuning that induces no data-frame loss, i.e., hitless λ-tuning, is essential in DWA. We derive requirements to prevent two types of upstream data-frame loss that the λ-tuning causes. To clarify the scalability of the hitless λ-tuning sequence against system parameters, we theoretically analyze the maximum input data rate to the optical network units (ONUs) to achieve λ-tuning without upstream data-frame loss while varying values for buffer size and λ-tuning time of the transceivers in ONUs and the DWA cycle. Then, using media access control boards that we developed for symmetric 40 Gbit/s λ-tunable WDM/TDM-PONs, we demonstrate hitless λ-tuning and confirm the validity of the theoretical analysis.