Etsuko Nomoto

12.5-gb/s direct Modulation up to 115/spl deg/C in 1.3-/spl mu/m InGaAlAs-MQW RWG DFB lasers with notch-free grating structure

Direct modulation at 12.5 Gb/s of 1.3-/spl mu/m InGaAlAs distributed feedback (DFB) ridge waveguide (RWG) lasers with low-resistance notch-free gratings running up to 115/spl deg/C is experimentally demonstrated. It was achieved by the combination of the high differential gain of an InGaAlAs MQW active layer, high characteristic temperature of RWG structure, and low-resistance notch-free grating. Moreover, successful transmission of 10-Gb/s modulated signals over 30-km standard single-mode fiber was achieved with the laser running at up to 115/spl deg/C. These results confirm the suitability of this type of laser for use as the cost-effective light source in 12.5-Gb/s and 10-Gb/s datacom applications.

115/spl deg/C, 12.5-Gb/s direct modulation of 1.3-/spl mu/m InGaAlAs-MQW RWG DFB laser with notch-free grating structure for datacom applications

Direct modulation at 12.5 Gb/s of 1.3-/spl mu/m DFB RWG lasers with low-resistance notch-free gratings running at 115/spl deg/C is experimentally demonstrated, for the first time. Moreover, 10-Gb/s modulated transmission over 30 km at 115/spl deg/C was achieved.

Experimental Demonstration of a Highly Reliable Multicore-Fiber-Based Optical Network

A prototype optical switch unit with multi-core fibers was fabricated. It was experimentally demonstrated that this prototype can automatically restore optical paths when line failure occurs. The corresponding restoration time is 5 ms, which meets the time specified in the ITU-T standard .

Multi-core fiber technology for optical-access and short-range links

To provide high-capacity/high-reliability optical-access and short-range links, a novel failure-recovery system utilizing protection optical switch units and multi-core fibers was developed. Configuring the proposed failure-recovery system, the developed multi-core fiber (MCF) connection technology (i.e., fan-in/-out modules and MCF connectors) and a protection optical-switch unit experimentally demonstrated automatic impairment-aware optical-switching.

Transmission properties of 1.3-/spl mu/m InGaAlAs MQW FP lasers in 10-gb/s uncooled operation

Limitations on transmission by an uncooled InGaAlAs Fabry-Perot (FP) laser in 10-Gb/s operation are experimentally and theoretically investigated. The InGaAlAs laser has both high relaxation-oscillation frequency and superior light-current characteristics over a wide temperature range, making it suitable for uncooled operation at 10 Gb/s. Over most of the temperature range used in transmission testing with standard-dispersion fiber, a small power penalty of 1 dB for a bit error rate (BER) of 10/sup -12/ was obtained in transmission over 4-7 km at the measured temperature range, whereas an error floor was seen in transmission over greater distance, despite the negative chromatic dispersion between the fiber and laser light. Theoretical analysis of these results indicates that mode-partition noise (MPN) imposes the major limitation on transmission distance. Moreover, the minimum transmission distance was estimated as 2.1 km, even when the production tolerance of lasing characteristics and zero-dispersion range of installed fiber are taken into account.

Automatic Impairment-Aware Optical Path Switching in Multicore Fiber Link Based on Multiring Structure

We developed a novel multicore fiber (MCF) link based on a multiring structure composed of field programmable gate array (FPGA)-based optical switching units for highly reliable networks. The switching algorithm implemented on the FPGA in the unit has five high-functioning processes capable of coping with multiple link failures in the network. To verify the operations of this MCF link, we experimentally demonstrated automatic impairment-aware optical path switching when a failure occurred in an MCF link based on a two-ring structure. We were able to perform path recovery by switching within a relatively short period of time, 7.6 ms, which is sufficiently less than that required by ITU-T. The restoration path that substitutes for the failed working path was also optimized for low-loss transmissions by selecting the path having the minimum number of units through which a signal passes. These results indicate that the link will be useful for optical network designs that simultaneously need to ensure high capacity and reliable transmissions in businesses such as data centers.

Experimental Evaluation of Recovery From Multiple Failures in Multicore Fiber Links Using FPGA-Based Optical Switch Units

We developed a novel failure recovery system utilizing a multicore fiber (MCF) link consisting of field programmable gate array (FPGA)-based optical switch (SW) units. A failure recovery scheme for managing the MCF link by means of monitoring signals (FRS-MS) was devised wherein the proprieties of the path usage are verified before the switching operation. It uses laser light signals to monitor protection paths in the MCF and selects the most available path as a protection path. Signal transmission experiments in point-to-point structures connected by an MCF link based on FRS-MS demonstrated that by switching in the event of multiple failures in the link, the path could be recovered within a short time period (approximately 8 ms). Performing a second (consecutive) switching after no signal was detected in the first switching in the event of other failures in the MCF link also led to recovery within a short time period (approximately 25 ms). These times are sufficiently less than that required by ITU-T. The results indicate that the MCF link and the FRS-MS operations embodied in FPGA-based SW units are useful for increasing the reliability of optical networks.

25 Gbps silicon photonics multi-mode fiber link with highly alignment tolerant vertically illuminated germanium photodiode

For a multi mode fiber optical link, a high speed silicon photonics receiver based on a highly alignment tolerant vertically illuminated germanium photodiode was developed. The germanium photodiode has 20 GHz bandwidth and responsivity of 0.5 A/W with highly alignment tolerance for passive optical assembly. The receiver achieves 25 Gbps error free operation after 100 m multi mode fiber transmission.

4-channel/spl times/10-Gbit/s parallel laser-diode module for high-capacity optical interconnects

A 4-channel/spl times/10-Gbit/s parallel LD module for next-generation high-capacity optical interconnects was developed. To suppress the inter-channel crosstalk, a PPLC platform with a channel-pitch conversion function was also developed. Four un-cooled 1.3-/spl mu/m InGaAlAs FP-LDs were mounted on separated electrodes of the PPLC platform by passive alignment; thus, the module is compact and low cost. Crosstalk is as low as -40 dB. The module has a total throughput of 40 Gbit/s over 300-m transmission without suffering any degradation caused by inter-channel crosstalk. Our proposed 4-channel/spl times/10 Gbit/s parallel LD module can be applied to next-generation high-capacity optical interconnects.

Experimental Evaluation of Recovery From Multiple Failures in Multicore Fiber-Based Optical Network

We experimentally investigate recovery from multiple link failures in a multicore fiber (MCF) link-based optical network (NW). The NW is composed of an input/output interface and a two-ring structure to achieve high-capacity and highly reliable NWs in access areas. Each node has a switch (SW) unit consisting of field-programmable gate array (FPGA)-based optical SW units. The SW unit is able to detect failures and implements a failure recovery scheme that monitors signals and secures a restoration path, even when there are multiple link failures. Signal transmission experiments demonstrated that the path could be recovered within a short time period (approximately 8 ms), even after multiple failures in the NW. Moreover, performing a second (consecutive) switching after no signal was detected in the first switching for complicated multiple failures in the NW also led to recovery within a short time period (approximately 25 ms). These times are sufficiently less than that required by recovery time standard for telecommunication NWs of the Telecommunication Standardization Sector of the International Telecommunication Union (ITU-T). The results indicate that the MCF link would be useful for increasing the reliability of NWs.