We experimentally demonstrate a directly modulated 1% AR-FPLA based ONU under side-mode injection-locking
for 1.25Gbits/s DWDM-PON application. With side-mode injection of this device, the characterizes of 34-channel
detuning capacity under self seeding and its corresponding to a wavelength locking range of 30 nm is a potential
candidate to achieve the cost effective and high capability 1.25 Gbits/s DWDM-PON systems. The effects of the
front-facet reflectivity in the AR-FPLA on injection locking range, spontaneous emission, and Q-factor are interpreted
from our results. A BER of <10-12 is obtained for the nearest 17 channels and a 10-10 error rate can be achieved for all
of the 34 injection-locked channels with SMSR >35dB, providing a negative power penalty of -0.7 dB.
22-channel detuning capacity of a 2.5Gbit/s directly modulated FPLD based ONU under side-mode
injection-locking for DWDM-PON is demonstrated with SMSR >35dB, Q-factor 6.8-9.2, locking range of 24nm, power
penalty of -0.7dB, and BER of 10-10 at -17dBm. The demonstrated side-mode injection-locked FPLD is a potential
candidate to achieve the cost effective and high capability 2.5Gbit/s DWDM-PON systems. The maximum usable ONU
channels of the side-mode injection-locking FPLD are 22, corresponding to a wavelength locking range of 24 nm.
Direct modulation of the upstream channels was successfully obtained and shows high quality eye diagram at ONU
transmission.
KEYWORDS: Signal to noise ratio, Picosecond phenomena, Signal attenuation, Signal processing, Eye, Semiconductor optical amplifiers, Tolerancing, Clocks, Optical amplifiers, Promethium
We demonstrate a novel all-optical RZ decision gate by using one dark-optical-comb injected SOA which is controlled by a reshaped optical clock with extremely high cross-gain-modulation (XGM) depth and narrow gain window. Such a decision gate exhibits improved 3R regeneration performances including timing tolerance of 33.5 ps, Q factor of 8.1 and extinction ratio of 13.6 dB. The correlation between backward injected dark-comb and input data wavelength region for optimizing the extinction ratio of the decision gated RZ data is determined. Under a threshold operating dark-optical comb power of 7 dBm, such a decision gate can recover the degraded RZ data with a bit-error-rate of less than 10-9 at 10 Gbits/s.
A coupling-ratio controlled wavelength tunable L-band erbium-doped fiber laser with tuning range of 45nm (1567 - 1612 nm), quantum efficiency of 42%, power conversion efficiency of 37%, tuning resolution of 0.3 nm is reported. The wavelength-tuning is achieved by a tunable band-pass filter (TBPF) or by adjusting the tunable-ratio optical coupler (TROC) without TBPF because of the difference of intracavity loss. The output wavelength can be tunable in the full L-band with TBPF, from 1567 to 1612 nm, and the pulse-width is <14.2 ps. Specially, during the wavelength-tunable process without TBPF, the modulation frequency of about 1 GHz remains unchanged and near-transform-limited pulses are generated by linear compression with 32.5 m single mode fiber (SMF) under 10% output coupling ratio.
A 30nm wavelength-tunable backward dark-optical-comb injection-mode-locked semiconductor optical amplifier fiber laser (SOAFL) with pedestal-free is reported after high-order soliton compression with maximum pulse compression ratio of up to 80. Shortest mode-locked SOAFL pulsewidth of 15 ps at 1 GHz is generated, which can further be compressed to 180 fs after linear chirp compensation, nonlinear soliton compression, and birefringent filtering. The pedestal-free eighth-order soliton can be obtained by injecting the amplified pulse with peak power of 51 W into a 107.5m-long single-mode fiber (SMF), providing a linewidth and timebandwidth product of 13.8 nm and 0.31, respectively. The tolerance in SMF length is relatively large (100-300 m) for obtaining <200fs SOAFL pulsewidth at wavelength tuning range of 1530-1560 nm. By extending the repetition frequency of dark-optical-comb up to 10 GHz, the mode-locked SOAFL pulsewidth can be slightly shortened from 5.4 ps to 3.9 ps after dispersion compensating, and further to 400 fs after second-order soliton compression. The lasing linewidth, time-bandwidth product and pulsewidth suppressing ratio of the SOAFL soliton become 4.5 nm, 0.33, and 10, respectively.
A novel top-illuminated In0.53Ga0.47As p-i-n photodiodes, with the partially p-doped photoabsorption layer, grown on GaAs substrate by using a linearly graded metamorphic InxGa1-xP (x graded from 0.49 to 1) buffer layer is reported. The dark current, optical responsivities, noise equivalent power, and operational bandwidth of the MM-PINPD with aperture diameter of 60 μm are 13 pA, 0.6 A/W, 3.4 times 10-15 W/Hz1/2, and 8 GHz, respectively, at 1550 nm. Under the illumination of 1.2-ps pulse-train, the measured impulse response is 41 ps and the frequency bandwidth is up to 8 GHz with heterodyne beating measurement. The low cost InGaAs photodiode with high current bandwidth product (350 mA times GHz, at 10 GHz) and bandwidth-efficient product (4.8 GHz times A/W) have been achieved.
A novel top-illuminated In0.53Ga0.47As p-i-n photodiodes (MM-PINPD) grown on GaAs substrate by using a linearly graded metamorphic InxGa1-xP (x graded from 0.49 to 1) buffer layer has been demonstrated on the SONET OC-192 receiving performance. With a cost-efficient TO-46 package, the MM-PINPD at data rate of 10 Gbit/s can be obtained at minimum optical power of -19.5 dBm. At wavelength of 1550nm, the dark current, optical responsivities, noise equivalent power, and operational bandwidth of the MM-PINPD with aperture diameter of 60 μm are 13 pA, 0.6 A/W, 3.4×10-15 W/Hz1/2, and 8 GHz, respectively. All the parameters are comparable to those of similar devices made on InP substrate or other InGaAs products epitaxially grown on an InGaAlAs buffered GaAs substrate. The performances of the MM-PINPD on GaAs are analyzed by impulse injecting of 1.2-ps pulse-train, eye pattern at 10Gbps, and frequency response from VNA.
The relationship between the backward optical injection waveform and the mode-locked pulse shape of semiconductor optical amplifier fiber laser (SOAFL) is studied. The SOA plays both the roles of a gain medium and an optically controlled modulator in this work. The injected optical comb-like bright and dark pulse-train with 60-ps pulsewidth was generated using a Mach-Zehnder intensity modulator (MZM) which DC-biased voltage of 1.7 V and 7.2 V, respectively. The backward injection of optical dark pulse-train results in a wide gain-depletion width (and a narrow gain window) within one modulation period, which is necessary for perfect mode-locking the SOAFL. In opposite, the backward injection of short optical pulse of bright optical pulse-train only causes a less pronounced gain-depletion effect. Such a broadened gain window can hardly initiate the mode-locking process. The backward comb-like dark pulse-train modulation is much easier to initiate harmonic mode-locking in the SOAFL than the bright pulse-train or sinusoidal-wave injection, which generates pulsewidth as short as 15 ps at 1 GHz. After propagating through 195m-long dispersion-compensating fiber, the pulsewidth of the mode-locked SOAFL can be linearly compressed to 13.5 ps. The linewidth and time-bandwidth product of the compressed SOAFL pulses are 1.78 nm and 0.8, respectively. The pulsewidth can further be nonlinearly compressed by using a 4695m-long single-mode fiber. The shortest mode-locked SOAFL pulsewidth of 3.5 ps at repetition frequency of 1 GHz by using cross-gain modulation technique is reported for the first time.
The sensitivity of SONET p-i-n photodiode receivers with transimpedance amplifiers (PIN-TIA) from OC-3 to OC-48 data rates, measured by using a standard bit-error-rate tester (BERT) and a novel sweep-frequency-modulation/intermixing (SMIM) technique, are compared. A threshold intermixed voltage below 15.8 mV obtained by the SMIM method corresponding to the sensitivity of the PIN-TIA receiver beyond –32 dBm determined by BERT for the SONET OC-48 PIN-TIA receivers with a required BER of better than 10–10 is reported. The analysis interprets that the intermixed voltage for improving the PIN-TIA receiver sensitivity from –31 to –33 dBm has to be increased from 12.5 to 20.4 mV. As compared to the BERT, the SMIM is a relatively simplified, fast, and low-cost technique for on-line mass-production diagnostics for measuring the sensitivity and evaluating the BER performances of PIN-TIA receivers.
The wavelength dependent mode-locking performances of a SOAFL under the backward optical injection via a sinusoidal-modulated distributed feedback laser diode (DFBLD) at 1 GHz repetition rate are characterized. The backward optical injection has to be sufficiently high to saturate a SOA and then depletes most of the excited state electrons in the SOA. In order to obtain shorter mode-locking pulsewidth, the DFBLD injecting wavelength should be slightly longer than the peak wavelength of SOA gain to benefit from shorter gain-recovery time and larger modulation depth. As the wavelength of a DFBLD approach the central wavelength of SOA, the shortest pulse was measured via a digital sampling oscilloscope (DSO). The pulses can also be obtained by DFBLD backward injection at 1535 nm in feedback of SOAFL, leading to the optimized pulsewidths of 22.7 ps.
A novel top-illuminated metamorphic In0.53Ga0.47As p-i-n photodiodes (MM-PINPD) grown on GaAs substrate by using a linearly graded InxGa1-xP (x graded from 0.51 to 1) buffer layer is reported. The dark current, optical responsivities, noise equivalent power (NEP), and operational bandwidth of the MM-PINPD with aperture diameter of 60 μm are 13 pA, 0.77/0.59 (1310/1550 nm) A/W, 6.9x10-11 W/Hz1/2, and 7.5 GHz, respectively. The performances of the MM-PINPD on GaAs are demonstrated to be better than those of a similar device made on InGaAs/InP substrate.
The sensitivity of SONET p-i-n photodiode receivers with transimpedance amplifier (PIN-TIA) from OC-3 to OC-48 data rates measured by using a standard bit-error-rate tester (BERT) and a novel synchronous-modulation inter-mixing (SMIM) technique are compared. A threshold inter-mixed voltage of below 15.8 mV obtained by SMIM method corresponding to the sensitivity of PIN-TIA receiver beyond -32 dBm determined by BERT for the SONET OC-48 PIN-TIA receivers with a required BER of better than 10-10 is reported. the analysis interprets that the inter-mixed voltage for improving the PIN-TIA receiver sensitivity from -31 dBm to -33 dBm has to be increased from 12.5 mV to 20.4 mV. As compared to the BERT, the SMIM is a relatively simplified and low-cost technique for on-line mass-production diagnostics for measureing the sensitivity and evaluationg the BER performances of PIN-TIA receivers.
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