Tunable Channel Spacing Research Articles

S/S+-band tunable dual-wavelength thulium doped fluoride fiber laser

A simple S/S+-band dual-wavelength thulium doped fluoride fiber laser (DWFL) with tunable channel spacing is demonstrated. The system utilizes a 24 channel arrayed waveguide grating to control the spacing between the two lasing wavelengths. The widest spacing that can obtained between two lasing wavelengths is 17.49 nm, while the narrowest is 0.75 nm. The cavity loss in the DWFL is controlled using two variable optical attenuators to equalize the power of the two lasing wavelengths. The DWFL has a maximum signal to noise ratio (SNR) of approximately 49.60 dB and good stability over long periods of operation, with only minor SNR fluctuations of less than 5.00 dB observed. The DWFL’s output also has side-mode suppression ratio (SMSR) of between 0.12 dB and 1.56 dB, indicating that there is little to no suppression of one wavelength over another, as well as a balanced power output that is highly desirable when used as reference or signal sources.

InGaAsP/InP Microring Resonator (MRR) Waveguide Used to Generate Soliton Comb with Tunable Channel Spacing

A novel system of tunable channel spacing soliton comb generation is presented using a PANDA ring resonator incorporated with an add-drop filter system. The intense optical fields known as soliton comb can be generated. Results show that soliton comb can be generated with un-equal spaced or variable free spectral range (FSR) by using the input bright soliton pulse into the microring resonator (MRR) system. The proposed comb filter exhibits a large tuning range in channel spacing. Our simulations shows that the channel spacing can be continuously tuned form up to 10 GHz, where the centre wavelength of the input power has been selected at 50 GHz. The structure of the proposed MRR's waveguide (InGaAsP/InP) and mode propagation profile have been presented in this research.

Channel-spacing tunable silicon comb filter using two linearly chirped Bragg gratings.

We propose a novel silicon-based comb filter with tunable channel spacing using a Michelson interferometer consisting of a pair of apodized linearly chirped Bragg gratings (ALC-BGs). The channel spacing of the proposed comb filter can be continuously tuned with a large tuning range by changing the effective refractive index of one of the ALC-BGs through the thermo-optic effect. Our numerical calculation shows that the channel spacing can be continuously tuned form 8.21 nm to 0.19 nm with an out-of-band rejection ratio of greater than 30 dB.

Photonic-Assisted Microwave Channelizer With Improved Channel Characteristics Based on Spectrum-Controlled Stimulated Brillouin Scattering

A photonic-assisted microwave channelizer with improved channel characteristics based on spectrum-controlled stimulated Brillouin scattering (SBS) is proposed and experimentally demonstrated. In the proposed system, N lightwaves from a laser array are multiplexed and then split into two paths. In the upper path, the lightwaves are modulated by a microwave signal with its frequency to be measured. In the lower path, for each lightwave, the wavelength is shifted to a specific shorter wavelength via carrier-suppressed single-sideband modulation and the spectrum is then shaped. The wavelength-shifted and spectrum-shaped lightwaves are used to pump a single-mode fiber to trigger SBS. Thanks to the SBS effect, multiple gain channels at the N wavelengths are generated. The channel profile of each channel, determined by the designed spectral shape of the pump source, is improved with a flat top and a reduced shape factor. The characteristics including the bandwidth, channel spacing, and channel profile can be controlled by adjusting the spectral shape of the pump source. A proof-of-concept experiment is performed. A microwave channelizer with a shape factor less than 2, a tunable channel bandwidth of 40, 60, or 90 MHz, and a tunable channel spacing of 50, 70, or 80 MHz, is demonstrated.

Dual-wavelength Brillouin ring-cavity fiber laser with tunable channel spacing

We experimentally demonstrate a dual-wavelength Brillouin fiber laser configured a pre-amplified Brillouin pump and FBG filter in a ring-cavity. The Brillouin laser can generate 21 Brillouin Stokes with 0.084 nm spacing, the first-Stoke has a peak power of 2.19 dBm. By adjusting the TLS wavelength and FBG’s reflection wavelength from circulating in the ring-cavity, the generated output dual-wavelength is stabile and the channel spacing is tunable, the widest and narrowest channel spacing obtained is approximately 1.12 nm (139 GHz) and 0.084 nm (10.5 GHz).

Reconfigurable All-Optical OTDM-to-WDM Conversion Using a Multiwavelength Ultrashort Pulse Source Based on Raman Compression

We propose and demonstrate a reconfigurable all-optical format conversion from optical time-division multiplexing (OTDM) to wavelength division multiplexing (WDM) providing full flexibility in terms of channel spacing and wavelength allocation. The system consists of a Raman amplification-based multiwavelength pulse compressor and a parametric sampling gate. Four conventionally generated WDM 10 GHz pulse trains are compressed at the same time to around 2.5 ps and, then, used for multiwavelength sampling of a 40 Gb/s 3.49 ps OTDM signal. Simultaneous extraction of all four 10 Gb/s tributaries to WDM channels in WDM grid with tunable channel spacing is demonstrated. Controlling time delays among the WDM clock channels makes it flexible to map OTDM tributaries onto any desired wavelength order, which is also called wavelength- and time-selective function. The reconfigurable functions can be realized independently on the coming OTDM signal by simply setting corresponding parameters of the WDM synchronous pulse trains at the terminals. This is also the key for the good overall performance obtained for all demultiplexed channels. Low power penalties below 1.9 and 2.1 dB are achieved with small penalty variations, 0.3 and 0.5 dB, among channels as the OTDM tributaries are converted to WDM grid with spacing of 400 and 200 GHz, respectively.

Reconfigurable multi-channel second-order silicon microring-resonator filterbanks for on-chip WDM systems

We report the fabrication of a reconfigurable wide-band twenty-channel second-order dual filterbank, defined on a silicon-on-insulator (SOI) platform, with tunable channel spacing and 20 GHz single-channel bandwidth. We demonstrate the precise tuning of eleven (out of the twenty) channels, with a channel spacing of 124 GHz (~1 nm) and crosstalk between channels of about -45 dB. The effective thermo-optic tuning efficiency is about 27 μW/GHz/ring. A single channel of a twenty-channel counter-propagating filterbank is also demonstrated, showing that both propagating modes exhibit identical filter responses. Considerations about thermal crosstalk are also presented. These filterbanks are suitable for on-chip wavelength-division-multiplexing applications, and have the largest-to-date reported number of channels built on an SOI platform.

Dual wavelength fibre laser with tunable channel spacing using an SOA and dual AWGs

In this paper, we propose and demonstrate a dual wavelength fibre laser (DWFL) based on the use of an inhomogeneously-broadened semiconductor optical amplifier (SOA) gain medium as well as two arrayed waveguide gratings (AWGs) together with two optical channel selectors (OCSs) and a broadband fibre Bragg grating (FBG) to generate dual wavelength output at variable channel spacings. The widest spacing obtained from the DWFL is 12.21 nm, while the narrowest spacing is 1.16 nm. The DWFL has good stability with only minor power fluctuations of less than 2 dB and a side mode suppression ratio (SMSR) of approximately 38.5 dB with fluctuations of less than 0.5 dB.

Tunable Channel Spacing of Dual-wavelength Erbium-doped Fiber Ring Laser using a Single Fiber Bragg Grating with Two Coil Heaters

Stable and tunable dual-wavelength erbium-doped fiber ring laser (EDFL) using a single fiber Bragg grating (FBG) and two coil heaters is proposed and demonstrated. Installing two identical coils into a single FBG, the FBG is symmetrically divided into two different portions. While a current supply to the coil, the refractive index of the FBG under the coil is changed. The FBG can operate as a joint of two different FBGs. Due to the thermo-optic effect of a fiber, the resonance wavelength split into two peaks. The spacing between two adjacent channels was changed as much as the difference of heating power. It was tuned up to 3 ㎚ of wavelength under the electrical power with a 1000 ㎽. Moreover, the lasing wavelength can be individually tuned without influencing to the adjacent channel.

Channel-spacing-tunable multi-wavelength fiber ring laser with hybrid Raman and Erbium-doped fiber gains

A multi-wavelength fiber ring laser of tunable channel spacing is proposed by employing an optical variable delay line (OVDL) in a Mach-Zehnder interferometer. Stable lasing is achieved at room temperature with the hybrid gains of a single mode fiber (as the Raman gain medium) and an Erbium-doped fiber (EDF) in a ring structure. The channel spacing of the present multi-wavelength fiber ring laser can be continuously tuned by adjusting the computer-controlled OVDL.