Will video caching remain energy efficient in future core optical networks？

Optical networks are expected to cater for the future Internet due to the high speed and capacity that they offer. Caching in the core network has proven to reduce power usage for various video services in current optical networks. This paper investigates whether video caching will still remain power efficient in future optical networks. The study compares the power consumption of caching in a current IP over WDM core network to a future network. The study considers a number of features to exemplify future networks. Future optical networks are considered where： （1） network devices consume less power, （2） network devices have sleep-mode capabilities, （3） IP over WDM implements lightpath bypass, and （4） the demand for video content significantly increases and high definition video dominates. Results show that video caching in future optical networks saves up to 42% of power consumption even when the power consumption of transport reduces. These results suggest that video caching is expected to remain a green option in video services in the future Internet.

Dynamic PMD compensation in 40-Gb/s optical communication system

A 40-Gb/s optical time division multiplexing (OTDM) return-to-zero (RZ) transmission experiments including a dynamic polarization mode dispersion (PMD) compensation was reported. The dynamic PMD compensator is made up of two-stage four degrees of freedom (DOF). The first stage adopts polarization controller and fixed time-delayed line. The second stage is variable differential group delay (DGD) element. The PMD monitoring technique is based on degree of polarization (DOP) as error signal. A novel practical adaptive optimization algorithm was introduced in dynamic adaptive PMD compensation. The experimental results show that the performance of the PMD compensator is excellent for 40-Gb/s RZ transmission systems with the large DGD. With this compensator, a significant improvement of system performance can be achieved in the eye pattern of a received signal. The first-order compensating ability of the compensator is greater than 30 ps. The second-order compensating ability is greater than 200 ps2. The first-order optimum compensating time is within 10 ms. The second-order optimum compensating time is within 24 ms.

Theoretical study of laser diodes with double optical feedbacks

A new set of nonlinear rate equations that can describe the external cavity semiconductor laser with two optical feedbacks is proposed. The dynamics of the semiconductor laser with two optical feedbacks are studied. It is found that when lasers are biased above the threshold and operate in regime V, another feedback can induce low frequency fluctuations.

Novel MEMS variable optical attenuator

A novel MEMS variable optical attenuator (VOA), which has completely different attenuation mechanism from those in literatures, is proposed and demonstrated in this paper. The basic operation principle is that the optical power coupled between two initially aligned single-mode fibers will be continuously attenuated while the end of one of the fibers is deflected from the initial position. A micromachined solenoid type inductor with a U-shaped permalloy magnetic core is used to attract the deflectable fiber that has a permalloy coat on its end. To fabricate the multi-layer three-dimensional inductive component, a new UV-LIGA process for thick photoresists is developed, combining advantages of both SU-8 and AZ-4000 series photoresists. The inductive component is approximately 1.7 mm×1.3 mm×50μm in size and has a low resistance value (- 2.1Ω). The whole size of the VOA before packaging is 30 mmx2 mmx0.6 mm. The first prototype shows less then 3-dB insertion loss at 0-dB attenuation and nearly 40-dB attenuation range with less than 20 mW electrical input power at wavelength 1550 nm.

8 × 10-Gb/s transmission system over 1500 km on G.652 fiber dispersion compensated by chirped fiber gratings

A low cost 8×10-Gb/s transmission system over 1500 km on conventional fiber using chirped fiber Bragg grating （CFBG） as dispersion compensator is demonstrated. The bit error rate （BER） below 10^-10 at 1500 km is obtained. The channel spacing is 0.8 nm and the optical amplifier spacing is 100 km. Only 16 erbium-doped fiber amplifiers （EDFAs） are used.

Design and parametric amplification analysis of dispersion-flat photonic crystal fibers

We present a modified method to design photonic crystal fibers (PCFs) with flattened dispersion char- acteristic. Using this modified PCF we design a broadband fiber optical parametric amplifier (FOPA), which provides a gain of 8 dB with 1.5-dB uniformity over a 260-nm bandwidth. Both the simulation results of total dispersion of PCF and the gain spectrum of FOPA are demonstrated.

High gain low noise L-band preamplifier with cascade double-pass structure

An optimized two-stage-cascade double-pass structure L-band preamplifier was proposed and experimentally studied to overcome the shortcomings of low gain coefficient and high noise figure of L-band erbiumdoped fiber amplifier (EDFA). The fiber lengthes of 6.5 and 32.5 m, pump powers of 130 and 119 mW for the first and second stages respectively are used in the experiment. When input signal power is-30 dBm, the amplifier can provide gain above 38.84 dB in a wavelength range of 34 nm (1568-1602 nm), gain ripple less than 2.04 dB (40.88-38.84 dB), and noise figures lower than 5.29 dB with the lowest value of 3.95 dB at 1590 nm. Experimental and simulation results show that this low cost and high pump efficiency amplifier is suitable for the application as an L-band preamplifier in the broadband fiber communication system.

Mixed heavy metal effect on emission properties of Er^(3+)-doped borosilicate glasses

Er3+-doped heavy metal borosilicate glasses were prepared using conventional melting and quenching method. The emission spectra of 4I13/2 → 4I15/2 transition were observed upon excitation at 974 nm and the lifetime of 4I13/2 level of Er3+ was measured. Based on these data, the fluorescence properties of Er3+ are investigated on the emission and gain characteristics at the 1.5 μm bands. In particular, the effect of relative heavy metal content on fluorescence properties is discussed.

Compact first and second order polarization mode dispersion emulator

We propose a 1st and 2nd order polarization mode dispersion emulator （PMDE） with one variable differential group delay （DGD） clement using birefringence crystals and four polarization controllers （PCs）. Monte Carlo simulations demonstrate that the output 1st and 2nd order polarization mode dispersion （PMD） generated by the PMDE consists with statistic theory. Compared with former PMDEs, this design is tunable, lower-cost, and more integrated for fabrication, which shows response time of 150μs, response frequency of 3.8 kHz, working wavelength of 1550 nm, total power consumption of less than 3 W, working range of 0 84 ps and 0 3600 ps^2 for 1st and 2nd order PMD emulation, respectively. Also, it is programmable and can be controlled by either singlechip or computer. It can be applied to study the outage probability of optical communication systems due to PMD effect and the effectiveness of PMD compensation.

Rational harmonic figure-eight actively-passively mode-locked erbium-doped fiber laser

The nonlinear optical loop mirror (NOLM) is used as a saturable absorbed to reshape pulses. Experimentally, an actively mode-locked erbium-doped fiber ring laser with figure-eight structure is set up. 2 - 4 order harmonic pulse train with stable amplitude has been obtained when the RF modulation frequency is about 2.5 GHz.

Multi-wavelength fiber source based on double-pass superfluorescent fiber source and a reflection Mach-Zehnder filter

A spectrum-sliced multi-wavelength fiber source (SS-MWFS) based on double-pass superfluorescent fiber source (SFS) with a reflection Mach-Zehnder filter (RMZF) as the reflected comb filter is demonstrated. With backward pumped configuration, MWFS with 50 wavelength channels of extinction ratio (ER) of 16.7 dB is obtained over the almost total C-band gain region. Total output power of the MWFS is 16.2 mW which shows that a power of about 0.3 mW of per channel is achieved. The SS-MWFS with forward pumped configuration is also discussed for comparing. The backward pumped configuration can provide a larger output power while only a little smaller ER than that of the forward pumped configuration.

1.3-μm uncooled 10 Gb/s directly modulated MQW AlGaInAs/InP laser diodes

In this paper, we report a novel 1.3-μm uncooled AlGaInAs/InP multiple quantum well （MQW） ridge waveguide laser diodes. By optimizing the design of MQW structure and facet coatings, together with the application of reversed-mesa ridge waveguide （RM-RWG） structure, polyimide planarization, and lift-off processes technology, an uncooled 1.3-μm, 10-Gb/s directly modulated MQW ridge waveguide laser diode was successfully fabricated. The threshold current and the slope efficiency were 7 mA and 0.48 mW/mA, respectively. The directly modulated bandwidths of 11 and 9.2 GHz were achieved at room temperature and 80℃, respectively.

A 2 by 2 wavelength tunable Fabry-Perot filter by using an electro-optic polymer film

A tunable Fabry-Perot (F-P) filter by using electro-optic polymer film is proposed. The electro-optic polymer is alkoxysilane dye (ASD)/SiO2-TiO2 hybrid material, whose electro-optic coefficient 733 is about 5 pm/V, The wavelength tuning range of 3.8 nm under 400-V DC voltage and the nonlinear characteristic with the electric field have been obtained via electro-optical properties of polymer. Both of polymer film fabrication and F-P filter design have been introduced. The tunable F-P filter is designed for the application of two-input/two-output port wavelength-selective optical switch. Also, some problems have been discussed in this letter.

Analysis of a one mirror inclined three-mirror cavity photodetector for high-speed application

There is a tradeoff between the quantum efficiency and the spectral response linewidth in resonant-cavity enhanced (RCE) photodetectors. Recently a new type of photodetector structure has been proposed, which utilizes an inclined mirror in a three-mirror cavity. It decouples the quantum efficiency and the spectral response linewidth and has high response speed, high quantum efficiency, and narrow linewidth simultaneously. The analysis result indicates that the linewidth of 0.8 nm and quantum efficiency higher than 70% can be achieved on this device. For a 30×30 μm2 device, the maximum bandwidth approaches 23 GHz.

Figure-eight actively-passively mode-locked erbium-doped fiber laser

The advantages of using nonlinear optical loop mirror (NOLM) to compress pulse with slight amplitude fluctuation and reflected energy loss are analyzed in theory. Experimentally the NOLM is placed in an actively mode-locked erbium-doped fiber ring laser to form a figure-eight actively and passively mode-locked fiber laser. 12 ps mode-locked pulses centered at 1.543 μm were obtained with the modulation frequency of 2.498748700 GHz. 3.715 mW output power is achieved with 50 mW pump power.