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This paper studies pattern effect of Semiconductor Optical Amplifier (SOA) at 25.78125 Gbps in 100GBASE-LR4 standard: 4 channels at 1295, 1300, 1305 and 1310 nm. Three issues are evaluated: input powers of SOA, different Pseudo-Random Binary Sequence (PRBS) patterns, and multi-channel amplification. Based on characteristic measurements of SOA, the maximum gain is 25 dB at 0.2-A current and 1310-nm input, showing 3-dB saturation gain at –15 dBm input power. The 3-dB gain spectrum is 20.9 nm wide center at 1311.5 nm wavelength. The OSNR (Optical Signal to Noise Ratio) is linearly proportional to SOA’s input power. The first issue, Bit Error Rate (BER) gets worse as SOA’s input rises into saturation region due to severe data pattern effect. For example, comparing among –17.5, –12.5 and –7.5 dBm inputs, the lower power gives less BER. Hence, the SOA is better applied as pre-amplifier. The second issue (PRBS: 7, 23 and 31), their corresponding BERs get worse with longer patterns. For instance, PRBS31 always shows higher BER, while PRBS7 can offer error-free transmission. The BER performance of Gigabit Ethernet link using 8b/10b coding is well estimated with PRBS7. The third issue, when 3 channels are added to 1310-nm main channel for SOA amplification, the BERs results have more power penalty than the 1-channel case due to XGM (Cross Gain Modulation) inside SOA. However, the SOA can operate as pre-amplifier in multi-channel transmission, such as to extend the 100GBase-LR4 (10-km limit) links to 100GBase-ER4 (40-km limit) without a replacement of expensive optical transceivers.

We measured the characteristics of Quantum Dot Semiconductor Optical Amplifiers (QD-SOA) with 25 stacked layers of InAs/InGaAlAs QDs grown on InP(311)B substrate. The temperature dependence of threshold current and lasing peak wavelength in C-band of QD-Laser Diode (QD-LD) were analyzed over its operating range of 15–80 °C. The chip gains of 3 device lengths (1.5, 2 and 2.4 mm) were compared under varied injected currents up to 500 mA. To avoid overheat and chip damage during measurements, the pulse current source with 1% and 10% duty cycles was used. Based on our best results of 2-mm long QD-SOA with 25 stacked QD layers, the 1% pulse is preferable because of its lower heating and additional chip gain of 11.9 dB. Hence, the highest chip gain of 35 dB was achieved at 400-mA injected current, as well as the highest 3-dB saturation output power at 20.9 dBm. According to the plot of chip gain versus wavelength, it shows 3-dB gain spectrum over 20 nm and the highest peak at 1570-nm wavelength with 500-mA injected current. In addition, the results of another QD-SOA module showed 15.4-dB Input Power Dynamic Range (IPDR), faster response time due to less pattern effect and error-free transmission of 40 Gb/s data over 20-km Single Mode Fiber (SMF) link.

Polarization Extinction Ratio (PER) is one of the key parameters for Polarization Maintaining Fiber (PMF) connector. Based on our previous studies, the bending radius of fiber greater than 1.5 cm will not affect the insertion loss of PMF [1]. Moreover, the measured PER of Panda PMF with LC/UPC connectors is more stable when that PMF is coiled around a hot rod with a minimum of 3-cm in diameter at 75°C temperature [2]. Hence, the hot rod with less constrained 6-cm in diameter at constant 75°C was selected for this PER measurement. Two PER setups were verified and compared for measuring LC/UPC PMF connectors. The Polarized Laser Source (PLS) at 1550 nm wavelength and PER meter from OZ Optics were used in both setups, in which the measured connector was connected to PLS at 0° angle while the other end was connected to PER meter. In order to qualify our setups, the percentage of Repeatability and Reproducibility (%R&R) were tested and calculated. In each setup, the PER measurement was repeated 3 trials by 3 appraisers using 10 LC/UPC PMF connectors (5 LC/UPC PMF patchcords with 3.5±0.5 meters in length) in random order. The 1st setup, PMF was coiled at a larger 20-cm diameter for 3 to 5 loops and left in room temperature during the test. The 2nd setup, PMF was coiled around a hot rod at constant 75°C with 6-cm diameter for 8 to 10 loops for at least 5 minutes before testing. There are 3 ranges of %R&R acceptation guide line

This paper shows the effect of bending radius and bending location on Insertion Loss (IL) in Single Mode Fibers (SMFs) and Polarization Maintaining Fibers (PMFs). Five FC/UPC PMF patchcords were tested for the effect of bending radius on IL, by being coiled from 0 (as reference) to 5 loops at bending radii of 7.5 mm to 17.5 mm in a step of 2.5 mm. Based on the significant IL changes at 7.5-mm radius and no change starting at 15-mm radius, these two radii were chosen for the study of bending location. Fifteen patchcords (5 FC/UPC PMF, 5 LC/UPC PMF and 5 LC/UPC SMF) were coiled for 1 full loop located at 20 cm to 100 cm in a step of 10 cm. At 7.5-mm radius, PMFs reveal their major IL variations strongly depending on bending location, while SMFs have minor variations. In contrast, no IL variations are observed at 15-mm radius for both PMFs and SMFs. This radius was then selected for the final study on a number of coils. All 15 patchcords were coiled up to 15 loops at 15-mm radius. The results exhibit insignificant IL increase for PMFs, but a small increase proportional to the number of coils for SMFs. Consequently, the benefit of these IL studies will validate the proper testing conditions for SMF and PMF patchcords, especially in PMFs, where the measurement of Polarization Extinction Ratio is correlated with IL.

We investigated the effect of Rapid Thermal Annealing (RTA) process on Quantum Dot Semiconductor Optical Amplifiers (QD SOAs). The devices are composed of 30-layer stacks of InAs quantum dot by using strain compensation method. The lateral size and height of QD are 30 nm and 4 nm, respectively. Our QD SOAs have emission wavelengths within 1.5 μm-band. We applied RTA process to improve the characteristics of internal quantum efficiency (ηi ) and optical loss (αi ) of ridge laser diode for QD SOAs. In this case, the operating temperatures of RTA process were set at 600°C, 620°C, 640°C and 660°C for 30 seconds each. In addition, the devices are cleaved to form a cavity length at 0.06 cm, 0.08 cm, 0.10 cm, 0.12 cm and 0.14 cm. According to the L-I characteristic result of ridge laser diode structure for QD SOAs at 640°C, the best minimum threshold current ( Ith ) is 47.93 mA. Moreover, according to the plot between 1 ηd−1 (external quantum efficiency) and cavity length, we can optimize the internal quantum efficiency and optical loss for a ridge laser diode structure to be 66.39% and 9.87 cm-1 respectively at 640°C RTA’s temperature. Finally, The RTA process helps to achieve 1.4 times higher in internal quantum efficiency as well as a minimal increase in internal optical loss comparing to without RTA.

This paper reports the temperature dependency of Polarization Extinction Ratio (PER) in Polarization Maintaining Fiber (PMF) with LC/UPC connectors. Ten LC/UPC PMF patchcords were PER measured under 3 testing conditions: A, B and C. Test A, patchcords were coiled on hot plate for 5 loops with 3-cm inner diameter and 4-cm outer diameter. The hot plate's temperature was increased from 25°C to 75°C and decreased back to 25°C at a step of 5°C. Test B, patchcords were coiled around hot rod with 3-cm in diameter for 5 loops. The hot rod's temperature was set in the same manner as Test A between 25°C to 100°C. In Test C, patchcords were uncoiled and left at room temperature while being PER measured for 15 minutes. From the sampled PER plots, small variations occur mainly at temperature transitions. The Standard Deviations (SDs) of PER confirm that their averages in Test A and B are nearly the same (0.30 – 0.35), but larger than the average SDs in Test C (0.17 and 0.21). However, when only the PERs below 35 dB (according to OZ Optics ER-100-IR specification) at 75°C in Test A and B are computed, their average SDs reduce to 0.08 and 0.06 respectively. Hence, the hot rod at constant 75°C is chosen for future PER measurement because of its stable results in shortest time and simplified setup.

This paper experimentally demonstrates the 10 Gb/s optical access network with downstream transmission at 1550-nm wavelength through a commercial EDFA in order to accomplish the maximum distance of 62 Km over SSMF and 256 subscribers. The theoretical analysis of three effects are considered: (1) link power budget from insertion loss of optical components, fiber's attenuation and an EDFA's gain, (2) pulse broadening due to Chromatic Dispersion (CD), and (3) added noises from APD and EDFA. The BER (Bit Error Rate) curves are computed in MATLAB and compared with experimental results when using two optical modulators: (1) EML (Electroabsorption Modulated Laser) with a fixed 8.69-dB Extinction Ratio (ER) and (2) Lithium-Niobate Mach-Zehnder Modulator (MZM) with an adjustable ER between 11.18 – 15.17 dB. Both computed and experimental BER curves prove that a higher ER via MZM gives a better BER than a lower ER fixed by EML. The experimental BER curves of full setup using EML shows its power penalty at BER 10−12 due to CD and ASE noise to be 0.34 dB and 0.38 dB respectively, whereas the full setup using MZM gives a slightly larger penalty of 0.69 dB and 0.56 dB respectively. Finally, when two TOBPFs (Tunable Optical Band Pass Filter) with 1-nm and 0.25-nm spectral widths are inserted after EDFA, the experimental BER curves show a slight improvement in power penalties of 0.03 dB and 0.15 dB respectively. Evidently, the narrower spectral width can remove ASE noise more effectively.