Abstract: A laser device includes front and back DBRs and an interferometer. The front DBR is coupled to a front DBR electrode. The front DBR forms a first tunable multi-peak lasing filter. The back DBR is coupled to a back DBR electrode. The back DBR forms a second tunable multi-peak lasing filter. The interferometer part is coupled between the front DBR and the back DBR. The interferometer part includes first and second waveguide combiners and first and second interferometer waveguides coupled therebetween. The first waveguide combiner couples the interferometer part to the back DBR. The second waveguide combiner couples the interferometer part to the front DBR. The first interferometer waveguide is coupled to an interferometer electrode. The interferometer forms a third tunable multi-peak lasing filter.

Abstract: A laser device includes front and back DBRs and an interferometer. The front DBR is coupled to a front DBR electrode. The front DBR forms a first tunable multi-peak lasing filter. The back DBR is coupled to a back DBR electrode. The back DBR forms a second tunable multi-peak lasing filter. The interferometer part is coupled between the front DBR and the back DBR. The interferometer part includes first and second waveguide combiners and first and second interferometer waveguides coupled therebetween. The first waveguide combiner couples the interferometer part to the back DBR. The second waveguide combiner couples the interferometer part to the front DBR. The first interferometer waveguide is coupled to an interferometer electrode. The interferometer forms a third tunable multi-peak lasing filter.

Abstract: An optical device comprises a light input, a light modulating means and a light output. The optical device further comprises an optical amplification device arranged to amplify light travelling between said light modulating means and said output. The optical amplification device comprises first and second serially connected post SOA (Semiconductor Optical Amplifier) units, each comprising at least one respective serially connected post SOA segment, which device is arranged to vary a light amplification by varying respective SOA bias voltages across said post SOA segments. A total SOA length of the first post SOA unit is relatively longer than a total SOA length of the second post SOA unit, which is relatively shorter. The optical device is arranged to, during operation using a particular operation program, always keep respective SOA bias voltages across each of the post SOA segments of the first post SOA unit at +0.5 V or more.

Abstract: A laser device includes front and back DBRs and an interferometer. The front DBR is coupled to a front DBR electrode. The front DBR forms a first tunable multi-peak lasing filter. The back DBR is coupled to a back DBR electrode. The back DBR forms a second tunable multi-peak lasing filter. The interferometer part is coupled between the front DBR and the back DBR. The interferometer part includes first and second waveguide combiners and first and second interferometer waveguides coupled therebetween. The first waveguide combiner couples the interferometer part to the back DBR. The second waveguide combiner couples the interferometer part to the front DBR. The first interferometer waveguide is coupled to an interferometer electrode. The interferometer forms a third tunable multi-peak lasing filter.

Abstract: An optical interference modulator comprises a main input, a main output, an optical splitter connected to the main input, first and second MMI couplers, each with a first primary-end access port connected to the splitter; a second primary-end access port connected to the main output; a first secondary-end access port connected to a respective primary waveguide; and a second secondary-end access port connected to a respective secondary waveguide. A light reflector is arranged to reflect light incident from said primary and secondary waveguides back into the same respective waveguide such that light travelling through the respective waveguide from the respective secondary-end access port, after reflection, travels back to the same secondary-end access port. For the MMI couplers, at least one of the respective primary and secondary waveguides comprises a respective light phase modulating device arranged to modulate the phase of light travelling along the corresponding waveguide in either direction.

Abstract: An optical interference modulator comprises a main input, a main output, an optical splitter connected to the main input, first and second MMI couplers, each with a first primary-end access port connected to the splitter; a second primary-end access port connected to the main output; a first secondary-end access port connected to a respective primary wave-guide; and a second secondary-end access port connected to a respective secondary wave-guide. A light reflector is arranged to reflect light incident from said primary and secondary waveguides back into the same respective waveguide such that light travelling through the respective waveguide from the respective secondary-end access port, after reflection, travels back to the same secondary-end access port. For the MMI couplers, at least one of the respective primary and secondary waveguides comprises a respective light phase modulating device arranged to modulate the phase of light travelling along the corresponding waveguide in either direction.

Abstract: An optical device comprises a light input, a light modulating means and a light output. The optical device further comprises an optical amplification device arranged to amplify light travelling between said light modulating means and said output. The optical amplification device comprises first and second serially connected post SOA (Semiconductor Optical Amplifier) units, each comprising at least one respective serially connected post SOA segment, which device is arranged to vary a light amplification by varying respective SOA bias voltages across said post SOA segments. A total SOA length of the first post SOA unit is relatively longer than a total SOA length of the second post SOA unit, which is relatively shorter. The optical device is arranged to, during operation using a particular operation program, always keep respective SOA bias voltages across each of the post SOA segments of the first post SOA unit at +0.5 V or more.

Abstract: Method for calibrating and tuning a part wise monotonically, continuously tunable semiconductor laser having a phase section and a first Bragg reflector section, through which sections a phase current and a first reflector current, respectively, are applied, which laser is not actively cooled, includes a) a calibration step, including obtaining at least two tuning lines along which tuning lines all combinations of phase and Bragg currents are stable operating points, identifying at least one reference stable operating point along a first one of the identified tuning lines at which operating point the laser emits light at a certain reference frequency, and storing at least one reference stable operating point; and b) a subsequent tuning step, during which the output frequency of the laser in relation to the reference frequency is controlled to a desired output frequency by translating the operating point of the laser along the first tuning line.

Abstract: Method for calibrating a tunable semiconductor laser having a phase section and a first Bragg reflector section, through which sections a phase current and a first reflector current, respectively, is applied, includes: a) selecting a phase current; b) identifying a range of reflector currents that achieves emission of light from the laser within a desired frequency band; c) scanning the reflector current(s) over the range of reflector currents, for each of at least two different phase currents, and reading the relative output power of the laser for each point scanned; d) identifying one stable operating point; e) identifying and storing one stable, continuous tuning line as constructed by interpolating; f) calibrating the laser frequency and observing a fed back signal from a target for the light emitted from the laser; g) measuring the temperature of the laser; and h) storing temperature and one operating point along the tuning line.

Abstract: Method for calibrating a tunable semiconductor laser having a phase section and a first Bragg reflector section, through which sections a phase current and a first reflector current, respectively, is applied, includes: a) selecting a phase current; b) identifying a range of reflector currents that achieves emission of light from the laser within a desired frequency band; c) scanning the reflector current(s) over the range of reflector currents, for each of at least two different phase currents, and reading the relative output power of the laser for each point scanned; d) identifying one stable operating point; e) identifying and storing one stable, continuous tuning line as constructed by interpolating; f) calibrating the laser frequency and observing a fed back signal from a target for the light emitted from the laser; g) measuring the temperature of the laser; and h) storing temperature and one operating point along the tuning line.

Abstract: Method for calibrating and tuning a part wise monotonically, continuously tunable semiconductor laser having a phase section and a first Bragg reflector section, through which sections a phase current and a first reflector current, respectively, are applied, which laser is not actively cooled, includes a) a calibration step, including obtaining at least two tuning lines along which tuning lines all combinations of phase and Bragg currents are stable operating points, identifying at least one reference stable operating point along a first one of the identified tuning lines at which operating point the laser emits light at a certain reference frequency, and storing at least one reference stable operating point; and b) a subsequent tuning step, during which the output frequency of the laser in relation to the reference frequency is controlled to a desired output frequency by translating the operating point of the laser along the first tuning line.

Abstract: Method for producing a modulated grating for an optimal reflection spectrum, which grating is a multiple wavelength reflector. The method includes the following steps: a) Determining wavelengths to be reflected b) Calculating a preliminary grating c) Comparing the reflection spectrum ro(f) with the characteristics of the wanted modulated grating d) Differences lead to a directional change of ro(f) e) Calculating a target function G(z) f) Changing the grating (zk) depending on the real and imaginary part of G(z) g) Repeating steps c) to f) until the grating reflects the predetermined wavelengths.

Abstract: An approach for compensating for losses in a tunable laser filter comprising includes providing a tunable waveguide material and an amplifying material that have different compositions. The tuning material and the amplifying material are placed parallel to one another. The amplifying material is disposed so that it covers the tuning material at discrete locations. Carriers are injected simultaneously into both materials. The tuning material is spaced from the amplifying material at an average distance that is greater than the charge carrier diffusion length, so as to reduce avoid diffusion of charge carriers from the tuning material into the amplifying material. This prevents the amplifying material draining the charge carriers out of the tuning material, thus enabling the refractive index of the tuning material to be tuned for a desired wavelength effect.

Abstract: A method of frequency and mode stabilizing a tuneable laser, wherein one or more measurable magnitudes is/are measured, wherein the laser has been characterized with respect to a number of operation points, and wherein the values of the measurable magnitude or magnitudes are stored in a microprocessor or corresponding device. The invention is characterized by causing the values of one or more of the measurable magnitudes to be non-extreme values; storing the values of such non-extreme values as a quotient where the numerator is the derivative of a measurable magnitude ?Y with respect to a control current ?I to one laser section, and where the denominator is the derivative of another measurable magnitude ?Z with respect to said control current ?I; and using the stored values to control the laser to a desired operation point.

Abstract: A method for frequency and mode stabilisation of a tuneable laser that has at least three sections, such as a Bragg laser or GCSR laser, where measurable magnitudes are measured and the laser has been characterised with respect to a number of operation points, and where the values of the measurable magnitudes are stored in a microprocessor or corresponding device. The invention is characterised in that the values of one or more of the measurable magnitudes (E) are caused to be non-extreme values; in that the measurable magnitudes include back power in addition to front power and frequency; and in that control currents (I1, I2, I3; I1, I2, I3, I4) for the gain section (P1), the phase section (N2; N3) and the reflector section (N3; N4) respectively of said laser, and when applicable also for the coupler section (N2) of said laser, are caused to be controlled on the basis of the measured values of said measurable magnitudes while keeping both the front power and back power constant.

Abstract: In a grating-assisted coupler, the mode of the first waveguide of the coupler may include some electric field in the second waveguide, with the effect that when light lasses from an input waveguide to the first waveguide, some light is launched, or injected, directly into the mode of the second waveguide. This injected light may or may not be in phase with the light subsequently coupled into the side of the second waveguide from the first waveguide via grating assistance. The grating structure is formed to ensure a desired phase relationship between the injected light and the grating coupled light: under certain conditions of relative phase, the transmission through the coupler may be increased and the bandwidth may be reduced.

Abstract: A tunable waveguide filter, formed from two waveguides, has an improved selectivity. The filter is tuned by passing a current through the filter. One of the waveguides is a semi-active waveguide. The increased absorption of charge carriers that occurs when current is injected into the semi-active waveguide is compensated by gain enhancement in the waveguide, because the material used for the semi-active waveguide is selected to provide an appropriate amount of gain. Therefore, the gain compensates for the losses that arise from free carrier absorption when the tuning current is applied to the filter.