An optical frequency COM generator generating an optical frequency COM having flat spectrum characteristics using a single modulator The optical frequency COM generator has a drive signal system (11) and a bias signal system (14) which drive a first drive signal (9), a second drive signal (10) and bias signals (12, 13) to satisfy the following expression (I) ΔA+Δt=π/2 (I) (where, ΔA and Δt are defined as ΔA≡(A1-A2)/2 and Δt≡(t1-t2)/2, respectively, A1 and A2 represent the amplitudes of the first and second drive signals when they are inputted to the electrodes of the first and second drive signals, respectively, and t1 and t2 represent the phases of bias voltages applied to first and second waveguides, respectively)

Super flat optical frequency comb signal generator

In a light control element comprising a thin plate having a thickness of 10 [mu]m or less and exhibiting electro optic effect, an optical waveguide formed on the thin plate, and a control electrode for controlling light passing through the optical waveguide, the control electrode includes a first electrode and a second electrode so arranged as to sandwich the thin plate, and the first electrode has a coplanar electrode consisting of a first signal electrode and a ground electrode, while the second electrode has a second signal electrode. Modulation signals having mutually inverted amplitudes are inputted to the first signal electrode of the first electrode and the second signal electrode of the second electrode such that the modulation signals cooperate to apply an electric field to the optical waveguide.

Optical Control Device

A Mach-Zehnder modulator has an optical splitting element splitting an input optical signal into two optical signals that are conveyed by two optical waveguide arms, and an optical combining element combining the two optical signals into an output optical signal. Two traveling wave electrodes (TWEs) carry an electrical modulation signal to induce a change in phase of these two optical signals, and include a number of pairs of modulation electrodes positioned adjacent to the waveguide arms. At least some of the electrodes in one waveguide arm have a different shape (e.g., length or width) than the electrodes in the other waveguide arm to alter the effectiveness of the electrodes in inducing a phase change in the two optical signals.

Traveling wave Mach-Zehnder optical device

The present invention discloses high-speed, single-drive and dual-drive external optical modulation devices that reduce the voltage and power required to amplify and modulate electrical signals onto an optical carrier. Two primary components of an optical transmitter, namely, the modulator and driver, are integrated, and preferably hybridly integrated, in a single package, thereby eliminating many of the cable connector interfaces that add loss, complexity and cost to the system. Further, integration frees the devices from the standardized impedance (i.e. 50 ohm) constraints that reduce performance, thereby enabling the design of optimized, low voltage, hybridly integrated modulation devices.

Hybridly integrated optical modulation devices

A heat exchanger ( 10 ) is provided and in a highly preferred form is an EGR cooler ( 52 ) having first and second passes ( 56 A, 56 B) that are connected to an inlet/outlet manifold ( 70 ) by a pair of corresponding thermal expansion joints ( 87,93 ) to allow differential thermal expansion between the various structural components of the heat exchanger ( 10 ).

2-pass heat exchanger including thermal expansion joints

A high-speed external optical modulator formed on a lithium niobate substrate has a diffused optical waveguide, a surface buffer layer, and electrodes for applying modulating RF energy. The electrodes are electroplated in at least two steps, resulting in a top co-planar waveguide structure lying on a second one. Low driving voltage is achieved through selection of the width, position, and dimension of the lower hot and ground electrodes. The upper ground electrodes and, preferably, also the upper hot electrode, are narrower in width than the corresponding lower electrodes, which helps to provide good velocity matching, good impedance values, and low electrical losses.

Electro-optic modulator having high bandwidth and low drive voltage

An optical modulator comprises a Z-cut lithium niobate substrate (21) on which is formed a Mach-Zehnder interferometer having two generally parallel waveguides (23, 25) lying beneath a buffer layer of dielectric material (27). First and second ground electrodes (29, 33) and a hot electrode (31) are disposed on the buffer layer (27), the first and second ground electrodes (29, 33) being spaced either side of the hot electrode (31), the hot electrode (31) and the first ground electrode (29) being proximate to at least apart of the respective waveguides (25, 23). The electrode structure is unsymmetrical in that (a) the hot electrode and the first ground electrode each have a width substantially less than that of the second ground electrode and or (b) the spacing between the first ground and hot electrodes is different from the spacing between the second ground and hot electrodes. whereby a range of chirp values can be obtained. When the spacing (G1) between the first ground and hot electrodes (29, 31) is smaller than the spacing (G2) between the second ground and hot electrodes (33, 31), and preferably the hot and first ground electrodes have a width not exceeding 15µm, the modulator is capable of operation at frequencies above 10GHz, possibly up to around 40GHz.

Lithium niobate optical modulator

An electro-optical modulator is disclosed that has a microwave input, chip with a thin film resistor or a lumped resistor located between an input RF connector and an RF electrode on a Lithium Niobate chip. The accessory connection chip has a broadband attenuator like a thin film resistor which is placed in a microstrip line for effecting the electrical transmission to Lithium Niobate chip. The insertion of the thin film resistor before the RF electrode lowers the electrical return loss value as a function of frequency, allowing a lower driving voltage design or a reduced chip length without degrading the performances.

System for reducing the electrical return loss of a lithium niobate traveling wave optical modulator with low characteristic impedance

The design and characterization of a dual-drive (DD) Z-cut Ti:LiNbO3 electrooptical modulator are presented. Both the radio frequency (RF) electrode layout and the optical splitters and combiners of the Mach-Zehnder interferometer are investi- gated: The former is designed to avoid RF line crosstalk, whereas the latter is to obtain a low-loss longitudinally short splitter struc- ture, able to properly separate the interferometer straight optical waveguide sections. First, the RF analysis is addressed, simulating the small-signal behavior of the DD coplanar waveguide electrode structure as a function of the central ground width. The perfor- mances of different splitter layouts (circular segment bends, sin- bends, and offset bends) are then investigated using the beam propagation method. Finally, experimental results on the electrical and optical test pattern structures, and of the DD Z-cut complete modulator, are discussed and compared with simulations. Index Terms—Coplanar waveguide (CPW), crosstalk, optical communication equipment, optical modulation.

Design and Characterization of a 10-Gb/s Dual-Drive

The design and characterization of a dual-drive (DD) Z-cut Ti:LiNbO/sub 3/ electrooptical modulator are presented. Both the radio frequency (RF) electrode layout and the optical splitters and combiners of the Mach-Zehnder interferometer are investigated: The former is designed to avoid RF line crosstalk, whereas the latter is to obtain a low-loss longitudinally short splitter structure, able to properly separate the interferometer straight optical waveguide sections. First, the RF analysis is addressed, simulating the small-signal behavior of the DD coplanar waveguide electrode structure as a function of the central ground width. The performances of different splitter layouts (circular segment bends, sin-bends, and offset bends) are then investigated using the beam propagation method. Finally, experimental results on the electrical and optical test pattern structures, and of the DD Z-cut complete modulator, are discussed and compared with simulations.

Design and characterization of a 10-Gb/s dual-drive Z-cut Ti:LiNbO/sub 3/ electrooptical modulator

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