CN1193471C - Irrelevant pulse semiconductor laser with low jitter frequency - Google Patents

Abstract

The present invention relates to an irrelevant pulse semiconductor laser with low jitter frequency, which belongs to the field of researches on optical communication and super fast phenomenon. In view of the defect of only being suitable for a plurality of fixedly repetitive frequencies of the prior art of reducing the pulse jitter of a gain switch semiconductor laser, the irrelevant pulse semiconductor laser with low jitter frequency is characterized in that one pulse semiconductor laser is used as a seed injecting source, and the pulse jitter of the main gain switch semiconductor laser can be reduced by the injecting method of outer pulses. When a seed pulse is injected in a 20 to 40 ps time window before the generation of a main pulse, a tunable irrelevant wavelength semiconductor laser pulse with the low jitter frequency can be generated. The irrelevant pulse semiconductor laser with low jitter frequency is a full optical fiber laser and has the advantages of simple operation, easy realization, wide application range, etc.

Description

Irrelevant pulse semiconductor laser with low jitter frequency

Technical field irrelevant pulse semiconductor laser with low jitter frequency of the present invention belongs to optical communication and ultrafast phenomena research field.

The pulse of background technology semiconductor laser is widely used among optical communication field and the ultrafast phenomena research, particularly use gain switch (electrical modulation) method to produce the semiconductor laser pulse, have advantages such as simple in structure, that volume is little, price is low, pulse repetition frequency is adjustable continuously, in optical communication, use gain-switching semiconductor lasers more at present as communication light source.But because the influence of spontaneous radiation in the laser chamber, gain-switching semiconductor laser has bigger interpulse time jitter usually, that is to say the instantaneous big rise and fall of light pulse repetition rate.For example, for gain switch distributed feed-back formula (DFB) semiconductor laser, the time jitter of its pulse is up to tens psecs (ps).Big shake can increase the error rate of high speed optical communication system.For example, for reaching 10 ^-12The error rate, the time jitter that requires light pulse is less than 1/14 of the pulse spacing.For optical time division multiplexing system, then require pulse jitter less than 1/20 of the pulse spacing.Like this, for the optical time division multiplexing system of 20Gb/s, the time jitter of light pulse should be lower than 2.5ps.The shake of light pulse is that the restriction optical communication is to a major obstacle of high speed development more.

Shake also can produce restriction to the application of ultrashort light pulse, for example in electro-optic sampling system based on ultrashort light pulse, the existence of shake has reduced the temporal resolution of measuring system, in measuring based on the pumping-detection of laser pulse probe, the existence of shake can reduce the signal to noise ratio of measuring system.

Research to laser pulse becomes a focus of research in recent years, at present people test discovery: by from seed or outside the continuous light injection technique can effectively reduce the pulse jitter of gain-switching semiconductor laser, from the seed injection technique is the partial pulse light of laser emitting to be reflected through the external reflection device again be injected in the laser chamber, and this technology that is injected in the chamber of laser own is called from the seed injection technique.Reduce the condition of shake from the seed injection technique: light pulse strictly equals the integral multiple of pulse period the two-way time in exocoel.This technology has an obvious defects: in case when external cavity length was determined, the repetition rate of gain-switching semiconductor laser just can not change, and repetition rate adjustable continuously be one of the main advantage of gain-switching semiconductor laser.Another technology that reduces shake is to inject with outside continuous light, but it requires expensive Wavelength tunable light source.In addition, we find in experiment, for gain switch Fabry-Perot laser, outside continuous light only injects and can increase pulse jitter, and can not reduce shake, from present experimental result, outside continuous light injects the reduction dither technique and only is adapted to the gain switch Distributed Feedback Laser.

Summary of the invention existing is subjected to light pulse repetition rate to limit this defective from the seed injection technique in order to overcome, and the invention discloses the technical scheme of irrelevant pulse semiconductor laser with low jitter frequency.

Irrelevant pulse semiconductor laser with low jitter frequency of the present invention is characterized in that the fine semiconductor laser of the magnetic tape trailer that matched by two wavelength forms an Optical Maser System by the fiber coupler coupling.One of them semiconductor laser injects the seed pulse source as the outside, be referred to as seed laser, the light pulse that seed laser produces partly is injected in another semiconductor laser cavity, the semiconductor laser that is injected by pulse is called main laser, does not need the built in light isolator in the chamber of main laser.Seed laser is made up of the semiconductor laser 4 and the temperature controller 12 thereof of the humorous modulating signal source 1 of adjustable repetitive frequency, broadband signal amplifier 2, T type biasing device 3 and direct current biasing power supply 15, magnetic tape trailer fibre.Dc bias current and modulation signal are added to by T type biasing device 3 on the semiconductor laser 4, produce the humorous seed pulse of adjustable repetitive frequency.Main laser is made up of the semiconductor laser 8 and the temperature controller 13 of modulating signal source 1, broadband electric delay line 5, broadband signal amplifier 6, T type biasing device 7, direct current biasing power supply 16, magnetic tape trailer fibre, dc bias current and modulation signal are added to by T type biasing device 7 on the semiconductor laser 8, produce the laser pulse of identical repetition rate.The shared same modulating signal source 1 of main laser and seed laser has identical clock reference to guarantee these two lasers.Seed laser and main laser all adopt the semiconductor laser of magnetic tape trailer fibre, and the tail optical fiber 17 of seed laser is connected by fiber coupler 10 with the tail optical fiber 18 of main laser.Seed pulse is injected in the main laser chamber by the port III of one group of offset controller 11 by fiber coupler 10, and the pulse of main laser output is by the port II outgoing of coupler 10.When in the seed laser during no optical isolator, an optical isolator 14 need be set between fiber coupler and seed laser, prevent that the pulse of main laser is injected in the seed laser chamber.Regulate modulation signal that electric delay line 5 makes main laser from modulating signal source 1 to semiconductor laser the transmission time t in 8 chambeies ₁, the modulation signal of seed laser is the transmission time t in 4 chambeies from modulating signal source 1 to semiconductor laser ₂With the transmission time t of seed pulse in tail optical fiber ₃, formula below satisfying:

t ₁(ps)+(30±10)ps＝t ₂(ps)+t ₃(ps)

Wherein: (30 ± 10) ps is the lead that seed pulse injects main laser.

Irrelevant pulse semiconductor laser with low jitter frequency of the present invention is characterized in that main laser can be single-mode laser or multiple die semiconductor laser.The outgoing wavelength of seed pulse when main laser is selected multimode laser for use can be realized the single mode output of tunable wave length.

Irrelevant pulse semiconductor laser with low jitter frequency of the present invention is characterized in that the wavelength of seed laser comes tuning by changing its working temperature.

Advantage of the present invention is an all optical fibre structure, and is simple in structure, easy to use, be easy to realize.The laser pulse of main laser output have tunable wave length, low jitter and with the characteristics such as repetition rate of light pulse.This laser can specifically be applied to fields such as optical communication, photoelectric measurement technology, ultrafast phenomena research, and its range of application covers industries such as communication, biology, material, electronics and industry.

Appended drawings is the structural representation of irrelevant pulse semiconductor laser with low jitter frequency.

Label in the accompanying drawing is:

1: microwave signal source, 2,6: wideband radio frequency amplifier, 3,7:T type biasing device, 4: semiconductor laser (seed laser), 5: the broadband electric delay line, 8: semiconductor laser (main laser), 9: same-phase power divider, 10: fiber coupler, 11: offset controller, 12,13 temperature controllers, 14: isolator, 15,16: DC power supply, 17: seed laser tail optical fiber, 18: the main laser tail optical fiber.

Embodiment is an example with two different semiconductor lasers of Fabry-Perot and DFB: the Fabry-Perot semiconductor laser of supposing no built-in isolator is a main laser, the dfb semiconductor laser that has the built in light isolator is a seed laser, the wavelength of two lasers is identical substantially, and two lasers are dc bias current in addition all.Produce the modulation signal of a certain frequency by an electrical modulation source, through same-phase power divider separated into two parts, a part of modulation signal is used to drive seed laser through broadband signal amplifier and T type biasing device and produces light pulse.Another part modulation signal affacts on the main laser through electric delay line, broadband signal amplifier and by T type biasing device.Main laser is operated under the stationary temperature by temperature controller, to guarantee not skew in time of wavelength.The working temperature of regulating seed laser makes the wavelength of its outgoing consistent with the centre wavelength of a longitudinal mode of main laser.The laser pulse of seed laser is by one group of Polarization Controller, through 10: 90 fiber couplers (according to the difference of injecting seed light power, can select the fiber coupler of different allotment ratios), 10% of seed pulse power is injected in the main laser chamber.If the length overall of the tail optical fiber of two-laser and fiber coupler is 2m, the refractive index n of optical fiber=1.53, the time that seed optical pulse is transmitted in tail optical fiber and coupler is:

Selecting electrical transmission speed for use is the transmission line of the BBC (broadband coaxial cable) of 0.7c (c is the light velocity in the vacuum) as electrical modulation signal, the transmission line of modulation main laser manys 2m than the transmission line of modulating seed laser, and modulation signal from the time difference of modulating signal source to two laser is:

$t_1-{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="C0213589200071.png"\; state="\{\{state\}\}">t</figure-callout>}}_2=\frac{2.1m}{0.7\&times;3\&times;{10}^{8}m/s}=1.0\&times;{10}^4\mathrm{ps}$

Regulate electric delay line, allow it produce the delay of 170ps, promptly satisfy formula: t ₁(ps)+(30 ± 10) ps=t ₂(ps)+t ₃(ps).The side mode suppression ratio of the light pulse of main laser this moment by fiber coupler port II outgoing surpasses 15dB, and pulse jitter reduces by 2～3 times, and the tuning range of repetition rate only is subjected to the restriction of selected photoelectric device bandwidth and the wavelength can be adjustable continuously in the 20nm scope.

Claims (1)

1. irrelevant pulse semiconductor laser with low jitter frequency, it is characterized in that the fine semiconductor laser of the magnetic tape trailer that matched by two wavelength forms an Optical Maser System by the fiber coupler coupling, one of them semiconductor laser injects the seed pulse source as the outside, be referred to as seed laser, the light pulse that seed laser produces partly is injected in another semiconductor laser cavity, the semiconductor laser that is injected by pulse is called main laser, do not need the built in light isolator in the chamber of main laser, seed laser is by the humorous modulating signal source of adjustable repetitive frequency (1), broadband signal amplifier (2), T type biasing device (3) and direct current biasing power supply (15), semiconductor laser of magnetic tape trailer fibre (4) and temperature controller (12) thereof are formed, dc bias current and modulation signal are added to by T type biasing device (3) on the semiconductor laser (4), produce the humorous seed pulse of adjustable repetitive frequency, main laser is by modulating signal source (1), broadband electric delay line (5), broadband signal amplifier (6), T type biasing device (7), direct current biasing power supply (16), semiconductor laser of magnetic tape trailer fibre (8) and temperature controller (13) are formed, dc bias current and modulation signal are added to by T type biasing device (7) on the semiconductor laser (8), produce the laser pulse of identical repetition rate, the shared same modulating signal source of main laser and seed laser (1), to guarantee that these two lasers have identical clock reference, seed laser and main laser all adopt the semiconductor laser of magnetic tape trailer fibre, the tail optical fiber of seed laser (17) is connected by fiber coupler (10) with the tail optical fiber (18) of main laser, seed pulse is injected in the main laser chamber by the port III of one group of offset controller (11) by fiber coupler (10), the pulse output of main laser is by the port II outgoing of coupler, when in the seed laser during no optical isolator, an optical isolator (14) need be set between fiber coupler and seed laser, the pulse that prevents main laser is injected in the seed laser chamber, the transmission time t1 of the modulation signal of main laser in, the modulation signal of the seed laser transmission time t in from modulating signal source (1) to semiconductor laser (4) chamber from modulation source (1) to semiconductor laser (8) chamber ₂With the transmission time t of seed pulse in tail optical fiber ₃, satisfy formula:

t ₁(ps)+(30±10)ps＝t ₂(ps)+t ₃(ps)

Wherein:

(30 ± 10) ps is the lead that seed pulse injects main laser.

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