Temperature-Dependent Gain Variation Reduction in$C$-Band Erbium-Doped Fiber Amplifier Using Phosphorus-Erbium-Doped Silica Fiber

We propose a new technique to reduce the temperature-dependent gain (TDG) tilt of erbium-doped fiber amplifier in the$C$-band by supplying a composite optical gain block, conventional aluminum-rich erbium-doped fiber (EDF) serially concatenated with a special EDF composed of phosphorus-doped silica host, which showed opposite TDG coefficients in the$C$-band. The TDG variation was suppressed to less than$pm$0.45 dB for the saturated gain of 16 dB in 1525–1565 nm, within the temperature range of$ -$40$^circ$C to$+$80$^circ$C.     

Suppression of temperature-dependent gain variation of conventional EDFA by hybrid connection of antimony-doped silica EDF

A new technique to suppress temperature dependence of EDFA gain is proposed and experimentally demonstrated. A specially designed EDF, the glass host of which is Sb-doped silica, showed an opposite sign of temperature dependent gain coefficients in C-band compared to Al-doped silica EDFs. Concatenation of those two EDFs showed an improved gain variation less than /spl plusmn/0.37 dB for the saturated gain over 15 dB, within -40 to +80/spl deg/C.     

On the Temperature-Dependent Gain and Noise Figure Analysis of C-Band High-Concentration EDFAs With the Effect of Cooperative Upconversion

We present an efficient temperature-dependent analysis to study the effect of cooperative upconversion on the temperature-dependent gain (TDG) performance of the C-band erbium-doped fiber amplifier (EDFA) at high-concentration. The influence of cooperative upconversion on the TDG is examined by using a set of temperature-dependent rate and light propagation equations. In the analysis given, the amplified spontaneous emission (ASE), as well as the excited state absorption (ESA) are also considered. In the forward pumping configuration at a signal wavelength of 1547 nm and in the temperature range of - 40degC to + 80degC, the variations of the TDG and the noise figure (NF) are about 1.7 and 0.9 dB, respectively. Numerical analysis results show that, with 260-mW/1480-nm pump power, an erbium-doped fiber amplifier having a doping concentration of 4.4 times 10²⁶ ion/m³ and optimum length of 9.2 cm may reach a signal gain of 44.6 dB and a noise figure of 3.9 dB at room temperature.     

A temperature-insensitive erbium-doped fiber amplifier for terrestrial wavelength-division-multiplexing systems

We have evaluated a variation in the temperature dependence of an erbium-doped fiber gain spectrum by a pump wavelength in the 980-nm band for the first time. By optimizing both the pump wavelength in the 980-nm band and a temperature-sensitive gain flattening filter, the gain change of an erbium-doped fiber amplifier was successfully suppressed to 0.18 dB/sub pp/ in the temperature range between 0/spl deg/C and 65/spl deg/C and the wavelength range of 37.0 nm.     

A standard fiber-based loop mirror as a gain-flattening filter for erbium-doped fiber amplifiers

We report flattening of the amplified spontaneous emission (ASE) spectrum from an erbium-doped fiber (EDF) using a standard fiber-based loop mirror (FLM), realized with an "over-coupled" fiber coupler. Through simulation, a bend-induced birefringent FLM as a gain-flattening filter is designed. Subsequently, an over-coupled coupler with a free spectral range of 140 nm is fabricated to realize the FLM, which is integrated to an EDF that is pumped by a 980-nm laser diode. By introducing an appropriate amount of bend-induced birefringence in the loop, the ASE spectrum of the EDF could be flattened within /spl plusmn/0.5 dB over a wavelength range of 32 nm in the C-band.     

Gain clamping in L-band erbium-doped fiber amplifier using a fiberBragg grating

A gain-clamping technique for the long wavelength band (L-band) erbium-doped fiber amplifier (EDFA) is presented. It uses a single fiber Bragg grating (FBG) on the input side of erbium-doped fiber (EDF) to inject a portion of backward conventional band (C-band) amplified spontaneous emission (ASE) back into the system. The use of a narrow-band (NB) FBG has shown a better performance in clamped-gain level and noise figure compared to a broad-band FBG. The amplifier gain for the NB FBG set up is clamped at 15.4 dB with a variation of less than 0.3 dB for an input power as high as 0 dBm     

A tunable S-band erbium-doped fiber ring laser

In this paper, we experimentally investigate and demonstrate an S-band erbium-doped fiber (EDF) ring laser based on an erbium-doped silica fiber and 980-nm pumping laser. Widely tunable range from 1480 to 1522 nm, and the sidemode suppression ratio (SMSR) of >30 dB/0.1 nm and the output power of >-2 dBm in the operating range from 1482 nm to 1517 nm have been achieved for this ring laser. Under the constant power control, the output power variation less than /spl plusmn/0.05 dB can also be accomplished over the tuning range from 1482 to 1517 nm. This S-band EDF ring laser is promising for the future S-band applications.     

1.14 b/s/Hz spectrally efficient 50/spl times/85.4-Gb/s transmission over 300 km using copolarized RZ-DQPSK signals

1.14 b/s/Hz spectrally efficient 50/spl times/85.4-Gb/s copolarized return-to-zero differential quaternary phase-shift keying (RZ-DQPSK) signals have been transmitted over 300 km of nonzero dispersion-shifted fiber (NZ-DSF), using optical prefiltering and conventional C-band erbium-doped fiber amplifier (EDFA) repeaters. In this study, in order to enhance the spectral efficiency, the impact of optical prefiltering on the RZ-DQPSK signal was experimentally investigated in comparison to the DQPSK signal, and we found that the RZ-DQPSK signal had better sensitivity with almost the same nonlinear tolerance than the DQPSK signal even with 65-GHz bandwidth optical prefiltering.     

Gain clamping in two-stage L-band EDFA using a broadband FBG

A gain-clamped long wavelength band erbium-doped fiber amplifier (L-band EDFA) with an improved gain characteristic is demonstrated by simply adding a broadband conventional band (C-band) fiber Bragg grating (FBG) in a two-stage amplifier system. The FBG reflects backward C-band amplified spontaneous emission (ASE) from the second stage back into the system to clamp the gain. The gain is clamped at about 22.4 dB with a gain variation below 0.4 dB for input signal powers of -40 to -15 dBm. Compared with an unclamped amplifier of similar noise figure values, the small signal gain has improved by 2.4 dB due to the FBG which blocks the backward propagating ASE. At wavelengths from 1570 to 1600 nm, gain of the clamped amplifier varies from 19.4 to 26.7 dB. The corresponding noise figure varies by /spl plusmn/0.35 dB around 5 dB, which is not much different compared to that of the unclamped amplifier.     

Measuring gain and noise figure of erbium-doped fiber amplifiers using a broad-band source and a transmission filter

We report a unique low-cost technique for measuring gain and noise figure (NF) in erbium-doped fiber amplifiers using a broad-band amplified spontaneous emission source and a transmission filter, by extracting the slope and intercept of output power spectral density versus input power spectral density at filter edges. The required filter depth is 30 dB. Discrepancies of /spl les/0.3 dB are found between gain or NF obtained from this technique and those measured using conventional spectral-interpolation technique employing multiple lasers at 100-GHz spacing across the C-band.     

Comparison of temperature dependence in C-band and L-band EDFAs

Temperature-dependent gain and noise characteristics of conventional band and long wavelength band erbium-doped fiber amplifiers are compared. Gain variations and noise figure penalties are shown for 980- and 1480-nm pump wavelength bands at different average inversion levels when the erbium coil temperature is cycled from -10°C to 80°C. Experimental results demonstrate that the L-band exhibits greater temperature-dependent gain and noise figure excursions compared to the C-band. Furthermore, it is shown that the impact of erbium coil temperature in the L-band is comparatively less dependent upon pump wavelength     

Improving the quantum efficiency of erbium-doped fiber laser by using a low-loss tipped fiber splicing process

A tipped single-mode fiber (SMF) structure is employed to reduce the fusion-splicing loss induced at the interface between SMFs and erbium-doped fibers (EDFs). By fusing the EDF and the tipped SMF with lens-like end face at once, the optimized fusion-splicing loss of as low as 0.2/spl sim/0.29 dB is obtained. An improvement on splicing loss of up to 0.46 dB is obtained as compared to the conventional EDF/SMF fusion geometry. The effects of tapered angle and radius of curvature at the end face of tipped fiber on the optimization of fusion-splicing loss are compared. The erbium-doped fiber laser with maximum quantum efficiency of 2.75% is reported by using the proposed splicing technology.     

Multiwavelength erbium-doped fiber lasers with active overlapping linear cavities

Multiwavelength oscillations in erbium-doped fiber (EDF) lasers with active overlapping linear cavities are investigated in detail. The laser can be designed to produce multiwavelength oscillations in the C-band and in the L-band. With a C-band three-wavelength laser, experiments show that the output powers of the lasing lines increase linearly or piecewise linearly with pump input. Any one lasing wavelength can be tuned over several nanometers depending on the gain tilt in the vicinity of the lasing wavelength while multiwavelength oscillation is still being maintained. The output power of any specific lasing line can be adjusted by suitably designing the EDF sections. This property also allows the laser to operate in multiwavelength switching mode. The laser exhibits a novel multiwavelength optical bistable behavior in the L-band. With an L-band dual-wavelength laser, the bistable input-output hysteresis behaviors of the two L-band wavelengths evolve in antiphase with respect to each other. The width of the bistable region has been increased to several tens of mW. It can be controlled and adjusted by the cavity loss and the EDF length. It is found that simultaneous L-band dual-wavelength oscillations can be obtained when part of the EDF, which functions as a saturable absorber, has been bleached. Moreover, simultaneous multiwavelength oscillations in both C-band and L-band have also been successfully demonstrated with the laser.     

Comparison of the static and dynamic properties of single- and double-pass partially gain-clamped two-stage L-band EDFAs

We investigate the static and dynamic properties of partially gain-clamped two-stage L-band erbium-doped fiber amplifiers (EDFAs) in single- and double-pass configurations. While both amplifiers can be designed to provide the same gain-clamped performance, the double-pass configuration requires /spl ap/40% less pump power and /spl ap/22% shorter length of EDF in the second stage, and has a corresponding improvement in power conversion efficiency of 45%, but at the expense of an increase in noise figure (/spl ap/0.5 dB) and dynamic gain variation.     

S-band single-stage EDFA with 25-dB gain using distributed ASE suppression

We propose a novel compact design for a single-stage S-band erbium-doped fiber amplifier, wherein distributed suppression of C-band amplified spontaneous emission is provided by optimized bend loss in a coaxial core fiber. Simulations show that /spl sim/25-dB unsaturated gain over 30-nm bandwidth (1495-1525) nm is achievable with the designed module, using a nominal pump power of 500 mW. The noise figure of the amplifier varies between 4.5 and 8 dB from 1495 to 1525 nm. By proper designing, we have also ensured that the gain ripple over the entire 30-nm bandwidth is 相似文献   

Coupled structure for wide-band EDFA with gain and noise figureimprovements from C to L-band ASE injection

We propose a novel structure for C plus L-band silica based wide-band erbium-doped fiber amplifiers (W-EDFA's), which use backward amplified spontaneous emission from the C-band EDFA as the pump-mediating injection source for the L-band amplifier unit. Experimental results show gain and noise figure improvements of over 2.6 dB and 0.6 dB, respectively, at -3.5 dBm of L-band input signal power. Spatially resolved numerical analysis confirms the pump-mediating effect of C-band backward ASE in the L-band EDFA for the gain and noise figure improvement, which also provides better understanding on the dynamics of C-band injection seed methods     

一种新型低噪声掺Er光纤放大器的研究

提出了一种新型的低噪声掺Er光纤放大器(EDFA)。将光波长交错器的输入端口与普通EDFA的输出端相连接,用于降低噪声,信号光由光波长交错器的偶信道端口输出。利用光波长交错器的梳状反射特性,抑制EDFA的放大自发辐射(ASE),改善EDFA的噪声特性,使其具有低噪声的特点。采用4m长的掺Er光纤(EDF)作为增益介质,小信号功率为-26dBm时,在1530～1560nm带宽范围内,测得低噪声EDFA的噪声系数低于3.83dB,仅比噪声系数的量子极限3dB大0.83dB。     

Serial topology of wide-band erbium-doped fiber amplifier for WDMapplications

We analyze the recently proposed serial topology of a wide-band erbium-doped fiber amplifier (EDFA) covering both the C- and L-bands and compare it with the parallel configuration of C-band and L-band amplifiers. The analysis is based on an application of a comprehensive large-signal numerical model, which takes into consideration propagation of wavelength-division multiplexing (WDM) signals, bidirectional pump, and both the downstream and upstream ASE power spectral components. We have found that in the multiwavelength regime the new topology can provide output power of 3 dBm/channel for 32 C-band and 40 L-band, 0.8-nm-spaced signals with reasonable pump powers to the first and the second stage. In comparison with the usual parallel configuration of C-band and L-band EDFAs, this topology saves about 20% of overall pump power, 10% of the necessary length of erbium-doped fiber (EDF) and achieves lower noise figure for L-band signals     

Air-core photonic-bandgap fiber-optic gyroscope

We report the demonstration of the first air-core photonic-bandgap fiber gyroscope. Because the optical mode in the sensing coil travels largely through air, which has much smaller Kerr, Faraday, and thermal constants than silica, far lower dependencies on power, magnetic field, and temperature fluctuations are predicted. With a 235-m fiber coil, we observe a minimum detectable rotation rate of /spl sim/2.7/spl deg//h and a long-term stability of /spl sim/2/spl deg//h, which are consistent with the Rayleigh backscattering coefficient of the fiber and comparable to that measured with a conventional fiber.     

PCB-compatible optical interconnection using 45/spl deg/-ended connection rods and via-holed waveguides

In this paper, a new architecture for a chip-to-chip optical interconnection system is demonstrated that can be applied in a waveguide-embedded optical printed circuit board (PCB). The experiment used 45/spl deg/-ended optical connection rods as a medium to guide light paths perpendicularly between vertical-cavity surface-emitting lasers (VCSELs), or photodiodes (PDs) and a waveguide. A polymer film of multimode waveguides with cores of 100/spl times/65 /spl mu/m was sandwiched between conventional PCBs. Via holes were made with a diameter of about 140 /spl mu/m by CO/sub 2/-laser drilling through the PCB and the waveguide. Optical connection rods were made of a multimode silica fiber ribbon segment with a core diameter of 62.5 and 100 /spl mu/m. One end of the fiber segment was cut 45/spl deg/ and the other end 90/spl deg/ by a mechanical polishing method. These fiber rods were inserted into the via holes formed in the PCB, adjusting the insertion depth to locate the 45/spl deg/ end of rods near the waveguide cores. From this interconnection system, a total coupling efficiency of about -8 dB was achieved between VCSELs and PDs through connection rods and a 2.5 Gb/s /spl times/ 12-ch data link demonstrated through waveguides with a channel pitch of 250 /spl mu/m in the optical PCB.