Wavelength Switching Operation Research Articles

Monolithically Integrated InP Bistable Photonic Waveguide Memory

In this article, we experimentally demonstrate, for the first time, an all-optical bistable monolithically integrated photonic waveguide memory of distinctive simplicity, relying on two travelling waveguide Semiconductor Optical Amplifiers with Cross Gain modulation (SOA-XGM) phenomena. Experimental proof-of-principle memory operation and wavelength switching operation are demonstrated at 5Gb/s, featuring an Extinction Ratio of 6 dB and a 4.6 dB BER penalty, in the case of the memory operation, as well as a power penalty of 3.5 dB at 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−9</sup> BER value, in the case of the wavelength switching. Being entirely designed and fabricated using standard library-based components, the proposed photonic memory fits within a 3.5 mm waveguide configuration of a generic monolithic InP platform, while its overall footprint is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.5\times 2$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> demonstrating a footprint reduction of 40% compared to previous hybrid SOA-MZI SR-FF architectures, holding the credentials for a fast photonic memory unit.

Switchable operation of multiple solitons and dissipative soliton resonance in a C- and L-band mode-locked fiber laser

We report on the wavelength-switchable operation of multiple solitons and dissipative soliton resonance (DSR) in C- and L-band fiber lasers. Mode-locking operations can be alternatively switched between 1565 nm and 1604 nm with adjustments to the polarization controller. Through controlling the intracavity filtering effect, tunable operations have been observed from 1563.7 nm to 1574.6 nm and from 1600.3 nm to 1605.7 nm. More importantly, the fiber laser operated at the 1565 nm waveband tended to generate multiple solitons, whereas one operated at the 1604 nm waveband tended to generate a rectangular DSR. Our investigations may contribute to understanding complex soliton dynamics in fiber lasers.

Wavelength Switchable Multi-Wavelength Erbium-Doped Fiber Laser Based on Polarization-Dependent Loss Modulation

We propose and demonstrate a novel and simple wavelength switchable multi-wavelength erbium-doped fiber (EDF) laser based on polarization-dependent loss (PDL) modulation with cascaded fiber Bragg gratings (FBGs) as the wavelength comb filter. PDL is generated and controlled by different polarization angles between the polarization state of each lasing line and the optical fiber polarizer in the laser cavity. The PDL modulation balances the difference between the total loss and the wavelength-dependent lasing gain. The relations among gain, loss, and laser output power under different PDL conditions are numerically analyzed on the basis of a simplified Giles model in an EDF laser system. Results show that multi-wavelength lasing lines can be built up by properly tuning the PDLs in different wavelengths. The amount of lasing lines can be switched by changing the PDL intensity in a certain wavelength. In an experiment, the PDL in that certain wavelength is modulated by utilizing four polarization controllable elements, each of which includes an FBG and a corresponding polarization controller (PC). One PC is used to control the polarization state of the reflected lasing line on the center wavelength of the FBG. A four-wavelength individually switchable EDF laser system is demonstrated by utilizing this wavelength switchable method, in which the switching operation for the single-, dual-, triple-, and four-wavelength laser output is verified. The experimental results are consistent with the theoretical results. All wavelength switching operations are conveniently controlled by merely adjusting the PCs. This simple structure and flexible wavelength switchable operations show that this multi-wavelength EDF laser has great potential in practical applications.

편광상이 고리 기반 광섬유 다파장 필터의 입력 편광으로 제어되는 채널 간격 스위칭에 대한 연구

In this paper, we propose an optical fiber multiwavelength filter based on a polarization-diversified loop (PDL), whose channel spacings (CSs) can be controlled by its input state of polarization (SOP). The PDL-based filter consists of a polarization beam splitter, three half-wave plates (HWPs), a Faraday rotator (FR), and two polarization-maintaining fiber (PMF) segments with equal birefringence and different lengths. At proper orientation angle sets (θ<SUB>h1</SUB>, θ<SUB>h2</SUB>, θ<SUB>h3</SUB>) of the three HWPs, the proposed filter can have its polarization-dependent transmittance, offering the CS-switchable operation realized by switching between two orthogonal input SOPs of linear horizontal polarization (LHP) and linear vertical polarization (LVP). In particular, at a fixed input SOP, a half-period wavelength switching operation, i.e., an interleaving operation, can also be implemented by controlling only one HWP angle (θ<SUB>h1</SUB> or θ<SUB>h3</SUB>). Theoretical prediction was verified by experiments. For orthogonal input SOPs of LHP and LVP, the fabricated PDL-based filter could provide transmission spectra with CSs of ∼0.9 and ∼0.3nm or vice versa at appropriate sets of (θ<SUB>h1</SUB><SUB></SUB>, θ<SUB>h2</SUB>, θ<SUB>h3</SUB>), respectively, and each of the transmission spectra could be interleaved by adjusting only θ<SUB>h1</SUB> or θ<SUB>h3</SUB>.

Wavelength-Switchable Fiber Laser Based on Long-Period Fiber Grating Written on Polarization-Maintaining Photonic Crystal Fiber.

Here we propose a wavelength-switchable erbium-doped fiber ring laser using a temperatureinsensitive spectral polarization-dependent loss (PDL) element and two fiber Bragg gratings (FBGs). The fiber PDL element was fabricated by inscribing a long-period grating (LPG) on polarizationmaintaining photonic crystal fiber (PMPCF) with a 10.6 μm CO₂ laser. The LPG fabricated on PMPCF, referred to as PMPCF-LPG, has the characteristics of a fiber polarizer at two specific wavelengths due to the birefringence of PMPCF and the co-directional mode coupling of the LPG. The two wavelengths at which the fabricated PMPCF-LPG acts as a polarizer are two resonance wavelengths (~1528.58 and ~1555.90 nm) of the PMPCF-LPG, obtained for orthogonal input polarization states. By considering these two resonance wavelengths of the PMPCF-LPG, the Bragg wavelengths of two FBGs, which determine lasing wavelengths in our wavelength-switchable laser, were selected as ~1527.71 and ~1554.74 nm. As the temperature sensitivity of the PMPCF birefringence is 30 times lower than that of the birefringence of conventional polarization-maintaining fiber (PMF), the fabricated PMPCF-LPG could facilitate more stable switching operation between the two lasing wavelengths in comparison with a previous fiber laser employing an LPG inscribed on conventional PMF as a wavelength-switching filter. The lasing wavelengths of our laser could be switched by controlling input polarization of the PMPCF-LPG with a polarization controller, and temperature-insensitive wavelength switching operation was experimentally demonstrated over a temperature range of 25-100 °C.

Four-wavelength-switchable SLM fiber laser with sub-kHz linewidth using superimposed high-birefringence FBG and dual-coupler ring based compound-cavity filter.

We propose and demonstrate a four-wavelength-switchable erbium-doped fiber laser (4WS-EDFL) with a four-channel superimposed high-birefringence fiber Bragg grating (SI-HBFBG) and a dual-coupler ring based compound-cavity (DCR-CC) filter. Both for the first time, a SI-HBFBG as a four-channel reflective filter is used in a multi-wavelength switchable fiber laser to define wavelength channels and a DCR-CC filter is used to select a single mode from dense longitudinal-modes in a fiber laser. We present in detail how to design, fabricate, and characterize the DCR-CC filter with both theoretical analysis and experimental results, which we believe is the first systematic approach for making a compound-cavity based filter used for selecting single-longitudinal mode (SLM) in a fiber laser. The enhanced polarization hole burning effect in a 2.9 m long erbium-doped fiber, coiled inside a three-loop polarization controller, and the polarization-mismatch-induced losses are introduced into the laser cavity to achieve wavelength-switching operations. We show that the 4WS-EDFL can be switched among fifteen lasing states, including four single-wavelength operations, six dual-wavelength operations, four three-wavelength operations and one four-wavelength operation, all with high stability. For demonstration, in switchable single-wavelength operations, the four SLM lasing outputs measured are all with an optical signal to noise ratio of >80 dB, a linewidth of <700 Hz, a relative intensity noise of ≤-156.7 dB/Hz at frequencies over 3 MHz, an output power fluctuation of ≤0.555 dB and excellent polarization characteristics.

Frequency Drift Reduction in a Four-Laser Array for TWDM PON Applications

Burst-mode operation of laser arrays suitable for next-generation passive optical networks (PON2) employing time and wavelength division multiplexing (TWDM) is impaired by frequency drifts under variable burst duration. In this work, the issue of frequency drifts under burst and wavelength switching operation is addressed in a four-laser array integrated with a multimode interference coupler using a regrowth-free technology. Frequency drifts are shown to be significantly reduced in a TWDM-PON configuration thanks to the introduction of a thermal management technique based on the use of inactive lasers in the array. Thanks to this method, up to 22% drift reduction is obtained under burst and wavelength switching operation.

Analysis of Bound-Soliton States in a Dual-Wavelength Mode-Locked Fiber Laser Based on Bi2Se 3

Wavelength switchable and dual-wavelength soliton operations are demonstrated in an erbium-doped fiber laser with three pieces of TI Bi2Se3 polyvinyl alcohol (Bi2Se3-PVA) film. Wavelength switchable operation from 1532 to 1557 nm could be achieved just by adjusting the pump power. With the appropriate settings of PC and pump power, a novel dual-wavelength soliton operation was observed. The dual-wavelength pulses operate at different mode-locked states. One is the single pulse mode-locking operation at 1532 nm, and the other one is the bound-soliton states at 1557 nm. However, the dual-wavelength soliton operation cannot be stable for a long time. The numerical results demonstrate that the separations of bound pulses have small variation and that the phase difference of bound pulses appear jumping change of $\pi $ .

Dual-Wavelength Harmonically Mode-Locked Fiber Laser With Topological Insulator Saturable Absorber

Dual-wavelength passively harmonic mode locking (HML) operation is demonstrated in an erbium-doped fiber laser with a microfiber-based topological insulator (TI) saturable absorber. It was found that the dual-wavelength pulse-trains possess different HML orders due to the different cavity nonlinear effects experienced by the two wavelengths. By properly adjusting the cavity parameters, dual-wavelength HML pulses with repetition rates of 388 and 239 MHz were achieved. Moreover, wavelength switchable operation of dual-wavelength HML pulses was also obtained. The experimental results reveal that the microfiber-based TI could indeed be employed as a high-performance dual-function photonic device with the saturable absorption and high nonlinear effects for the applications in fields of ultrafast and nonlinear photonics.

A switchable multiwavelength fibre laser with polarization-maintaining erbium fibre

A multiwavelength fibre laser with wavelength-switchable operation has been demonstrated, utilizing the combined effects of polarization hole burning and intensity-dependent transmission. Polarization-maintaining erbium fibre (PM-EDF) with an anisotropic gain is used as the gain medium to suppress the mode competition. Simultaneously, the PM-EDF and the polarizer in the cavity form an equivalent periodic filter. Four lasing wavelengths simultaneously oscillating are obtained, which are stable over an hour at room temperatures. Furthermore, by adjusting the polarization controllers the laser can also produce triple-, dual- and single-wavelength lasing oscillations, which can be switched among the four simultaneously oscillating wavelengths.

Tuning and wavelength switching erbium-doped fiber ring lasers by controlled bending in arc-induced long-period fiber gratings

In this paper, we report a simple method for the production of an all-fiber, tunable and wavelength switchable erbium-doped fiber ring laser (EDFRL). We use the shift in resonance wavelength and notch-depth of arc-induced long-period fiber gratings (LPFGs) when it is subject to controlled bend to suppress some wavelength gain and promote lasing in a selective way in a fiber laser system. By changing the bending radius, the operating wavelength of the EDFRL can be tuned from 1526 to 1538nm and then switched and tuned from 1568 to 1557nm. The maximum separation measured between laser lines was ∼42nm. This is one of the highest laser separations reported in a wavelength switching operation of an EDFL using a single LPFG as wavelength selective filter.

Switchable dual-wavelength erbium-doped fiber laser based on polarization-maintaining fiber Sagnac loop mirror and fiber Bragg gratings

A switchable dual-wavelength erbium-doped fiber laser is proposed and experimentally demonstrated, which is constructed by a polarization-maintaining fiber Sagnac loop mirror (PMF-SLM) and two FBGs with different wavelengths. Wavelength switching operation is achieved by properly adjusting the polarization controller (PC) in the PMF-SLM. Stable single- or dual-wavelength lasing output can be realized. The maximum amplitude variation for every lasing wavelength is less than 1 dB, and the signal-to-amplified spontaneous emission (ASE) ratio is about 35 dB.

Wavelength-dependent selective loss for wavelength switching operation of an erbium-doped fiber ring laser

A wavelength-switchable erbium-doped fiber ring laser based on a wavelength-dependent selective loss fiber filter is demonstrated and reported. The filter is based on a long-period fiber grating and bending loss. The operating wavelength of the fiber laser can be switched from a single-wavelength operation at 1565 to 1527 nm.

Switchable multiwavelength erbium-doped fiber laser employing wavelength-dependent loss

A novel switchable multiwavelength erbium-doped fiber laser (EDFL) is proposed and demonstrated based on two comb filters. One comb filter is used to define the wavelength spacing, the other filter with a very narrow wavelength spacing is used to induce wavelength-dependent loss (WDL) effect to suppress the mode competition caused by homogeneous gain broadening of the erbium-doped fiber (EDF). As a result, triple-wavelength lasing operation with wavelength spacing of 0.8 nm has been achieved. Wavelength switching operation of the laser was also obtained by adjustment of a polarization controller (PC) in the cavity. The measured power fluctuation of each wavelength is less than 0.4 dB.

Tunable and Switchable Multiwavelength Passively Mode-Locked Fiber Laser Based on SESAM and Inline Birefringence Comb Filter

A tunable and switchable multiwavelength passively mode-locked fiber laser by using a semiconductor saturable absorber mirror (SESAM) and an inline birefringence fiber filter is proposed and demonstrated. By properly rotating the polarization controllers (PCs), up to 7-wavelength mode-locked pulses in 3-dB bandwidth with 3.65-nm channel spacing are obtained. The wavelength switchable operation is determined by the characteristics of the comb filter used in the experiment. Taking advantage of an intensity-dependent loss mechanism caused by the nonlinear polarization rotation (NPR) effect, the mode competition is efficiently suppressed. In addition, the lasing locations of multiwavelength mode-locked pulses can be flexibly tuned via the wavelength-dependent loss mechanism.

Investigation of Improvement of Dynamic Switching Operation for Wavelength Switch With Super-Structure-Grating (SSG)-DBR-LD, Delayed-Interference Signal-Wavelength Converter (DISC), and Bandpass Filter

We demonstrate dynamic wavelength switching operation using a super-structure grating (SSG)-DBR-LD and a semiconductor optical amplifier (SOA)-delayed-interference signal-wavelength converter (DISC) for optical packet switch and buffering systems. The wavelength conversion-type optical switch has the advantage of lowering packet blocking probability and reducing numbers of the required SOAs in the DISC-type wavelength converter. However, we confirmed that large optical spikes occur at the timing of wavelength switching due to the optical chirping. By detuning the center wavelength of a bandpass filter to suppress optical chirped wavelength component, we could reduce the intensity of the spikes. We also observed the alternate wavelength switching operation with small optical spikes with fixed detuning of the bandpass filter and the fixed optical phase bias of the Mach-Zehnder Delayed Interferometer (MZDI) by setting the small current variation of the SSG-DBR-LD for wavelength switching. Error free performance was also achieved under back-to-back and 50 km single mode fiber transmission.

Wavelength switchable all-fiber comb filter using a dual-pass Mach-Zehnder interferometer and its application in multiwavelength laser

A novel wavelength switchable all-fiber comb filter based on a dual-pass Mach-Zehnder (M-Z) interferometer is proposed and demonstrated. The proposed filter consists of a rotatable polarizer and a standard dual-pass M-Z interferometer composed of two 3-dB fiber couplers with a polarization controller (PC) in one arm. When the PC is properly set, the wavelength switchable operation is achieved by adjusting the polarization state of the input light. Theoretical calculation is verified by the experimental results. As applications, the proposed comb filter is incorporated into a fiber ring laser to generate wavelength switchable multiwavelength lasing.

Polarization-Controlled Tunable All-Fiber Comb Filter Based on a Modified Dual-Pass Mach–Zehnder Interferometer

We propose and demonstrate a novel tunable all-fiber comb filter based on a modified dual-pass Mach-Zehnder (M-Z) interferometer. The proposed filter consists of a polarization-dependent isolator, a polarization controller (PC), and a modified dual-pass M-Z interferometer composed of a standard 3-dB and a non-3-dB fiber coupler with a PC in one arm. By adjusting the polarization state of the input light, dual-function operation, the spectral spacing tunable and the wavelength switching (interleaving) operation can be easily achieved. The theoretical prediction is verified by the experimental results.

Two-wavelength switching with 1550 nm semiconductor laser amplifiers

Feature Issue on Photonics in SwitchingTwo-wavelength switching operation between two signals at different wavelengths is reported using the optical bistability occurring in two different semiconductor laser amplifiers. With this technique an optical signal can be set in either of the optical input wavelengths by appropriate choice of the powers of the input signals. Switching of a signal beam by another control beam at different wavelength is reported experimentally with a 1550 nm distributed feedback semiconductor optical amplifier. Also, a theoretical model has been generated to analyze the wavelength switching operation with a novel amplifier type--the 1550 nm vertical cavity semiconductor optical amplifier (VCSOA). Using a 1550 nm VCSOA, wavelength switching operation is reported with a calculated input power below 1 μW. This low input power requirement for switching added to the high-frequency response of the VCSOA, and the ease of fabricating 2D arrays of these devices due to the vertical structure, makes the VCSOA a very interesting device for use in optical switching applications in the optical telecommunication networks.

Wavelength switching in an actively mode-locked Fabry-Perot laser diode with a highly dispersive external cavity

We demonstrate a simple and reliable scheme for wavelength switching in an actively harmonic mode-locked Fabry-Perot laser diode (FPLD) that is coupled to a highly dispersive external fiber cavity. Wavelength switching between FPLD modes is achieved by detuning of the modulation frequency applied to the FPLD. A side-mode suppression ratio of as much as 40 dB is maintained, and the supermode noise suppression ratio is more than 50 dB for the whole wavelength switching operation range of 4.7 nm when the pulse repetition rate is ~2 GHz. The wavelength-switching mechanism of our laser is based on the wavelength-dependent cavity resonance frequency shift that is due to chromatic dispersion, and we verify that our experimental results closely coincide with analytical results.