fiberassign-TILEID.fits.gz

Summary:

The fiberassign file contains the fiber positioner configuration information for each exposure: what fiber is placed where, what target that is, etc.

Naming Convention:

fiberassign-TILEID.fits.gz, where TILEID is the zero-padded 6-digit tile ID. Some early versions were not compressed.

Regex:

fiberassign-[0-9]{6}\.fits\.gz

File Type:

FITS, 5 MB

Contents

Number	EXTNAME	Type	Contents
HDU0	PRIMARY	IMAGE	Keywords only
HDU1	FIBERASSIGN	BINTABLE	Target assignments for each fiber
HDU2	SKY_MONITOR	BINTABLE	Sky location for the 20 sky monitor fibers used by the ETC
HDU3	GFA_TARGETS	BINTABLE	Selected star for the ETC / GUIDE / FOCUS
HDU4	TARGETS	BINTABLE	List of targets that are reachable by a positioner
HDU5	POTENTIAL_ASSIGNMENTS	BINTABLE	All possible (TARGETID, FIBER, LOCATION) assignments

FITS Header Units

HDU0

EXTNAME = PRIMARY

No data, but some useful header keywords.

Required Header Keywords

Required Header Keywords Table

KEY	Example Value	Type	Comment
TILEID	4403	int	Tile ID
TILERA	170.239	float	[deg] Tile Right Ascension
TILEDEC	-7.093	float	[deg] Tile Declination
FIELDROT	0.0210480650645507	float	[deg] Field rotation
FA_PLAN	2022-07-01T00:00:00.000	str	[UTC] Plan field rotations for this date
FA_HA	-6.72	float	[deg] Design Hour Angle
FA_RUN	2022-01-03T17:00:31+00:00	str	[UTC] Date of the loaded Focal Plane state
FA_M_GFA	0.4	float	[mm] Margin around GFA keep-out polygons
FA_M_PET	0.4	float	[mm] Margin around petal-boundary keep-out polygons
FA_M_POS	0.05	float	[mm] Margin around positioner keep-out polygons
REQRA	170.239	float	[deg] Tile Right Ascension
REQDEC	-7.093	float	[deg] Tile Declination
FIELDNUM	0	int	Not used, always zero
FA_VER	5.4.0	str	Fiberassign code version
FA_SURV	main	str	Survey of origin of the targets
FAFLAVOR	maindark	str	String composed of the SURVEY and the PROGRAM
DESIROOT	/data/datasystems	str	DESI_ROOT environment variable path
GFA	DESIROOT/target/catalogs/dr9/1.1.1/gfas	str	Path to the input GFA targets
MTL	DESIROOT/survey/ops/surveyops/trunk/mtl/main/dark	str	Path to the primary targets ledgers
SCND	DESIROOT/target/catalogs/dr9/1.1.1/targets/main/secondary/dark/targets-dark-secondary.fits	str	Path to the secondary targets static catalogs
SCND2	DESIROOT/target/catalogs/dr9/1.1.1/targets/main2/secondary/dark/main2targets-dark-secondary.fits	str	Path to the secondary targets static catalogs
SCNDMTL	DESIROOT/survey/ops/surveyops/trunk/mtl/main/secondary/dark	str	Path to the secondary targets ledgers
SKY	DESIROOT/target/catalogs/dr9/1.1.1/skies	str	Path to the sky targets
SKYSUPP	DESIROOT/target/catalogs/gaiadr2/1.1.1/skies-supp	str	Path to the supp-sky targets
TARG	DESIROOT/target/catalogs/dr9/1.1.1/targets/main/resolve/dark	str	Path to the primary targets static catalogs
TOO	DESIROOT/survey/ops/surveyops/trunk/mtl/main/ToO/ToO.ecsv	str	Path to the Target-of-Opportunity catalog
FAARGS	–doclean n –dr dr9 –dtver 1.1.1 –gaiadr gaiadr2 –goaltime 1000.0 –ha -6.72 –hdr_faprgrm dark –hdr_survey main –log_stdout False –lookup_sky_source ls –margin_gfa 0.4 –margin_petal 0.4 –margin_pos 0.05 –mintfrac 0.85 –mtltime 2022-01-13T18:13:09+00:00 –nosteps qa –pmcorr n –pmtime_utc_str 2022-01-14T10:13:28+00:00 –program DARK –rundate 2022-01-03T17:00:31+00:00 –sbprof ELG –sky_per_petal 40 –sky_per_slitblock 1 –standards_per_petal 10 –steps tiles,sky,gfa,targ,scnd,too,fa,zip,move,qa –survey main –svntiledir /data/tiles/SVN_tiles –tiledec -7.093 –tileid 4403 –tilera 170.239 –worldreadable True	str	fba_launch command arguments
OUTDIR	/data/datasystems/target/fiberassign/holding_pen/	str	Folder where the fba_launch outputs are written
SURVEY	main	str	Survey of origin of the targets
NOWTIME	2022-01-14T10:13:28+00:00	str	[UTC] Date of the fba_launch call
RUNDATE	2022-01-03T17:00:31+00:00	str	[UTC] Date of the loaded Focal Plane state
PMCORR	n	str	Is proper-motion correction applied for stars?
PMTIME	2022-01-14T10:13:28+00:00	str	[UTC] Used current time, if proper-motion correction is applied
FAPRGRM	dark	str	Program to which this tile belongs
MTLTIME	2022-01-13T18:13:09+00:00	str	[UTC] Date used to read the ledgers
OBSCON	DARK|GRAY|BRIGHT|BACKUP	str	Allowed observing conditions for this tile
GOALTIME	1000.0	float	[s] Aimed EFFTIME_SPEC
GOALTYPE	DARK	str	Sky conditions used for some noise estimation
EBVFAC	1.08401875659818	float	10.0 ** (2.165 * median(EBV) / 2.5))
SBPROF	ELG	str	Source profile used for some noise estimation
MINTFRAC	0.85	float	Fraction of GOALTIME to be reached by EFFTIME_SPEC to consider the tile has completed
FASCRIPT	/software/datasystems/desiconda/20200924/code/fiberassign/5.4.0/bin/fba_launch	str	Path to the fba_launch used script
SVNDM	138481	str	DESIMODEL/data svn revision number
SVNMTL	1083	str	DESI_SURVEYOPS/mtl svn revision number
LKSKYSRC [1]	ls	str	Photometric survey used for the sky look-up table for the stuck fibers

[1]

Optional

Empty HDU.

HDU1

EXTNAME = FIBERASSIGN

The target assignments for each fiber of this tile.

Required Header Keywords

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	293	int	width of table in bytes
NAXIS2	5000	int	number of rows in table
TILEID	4403	int	Tile ID
TILERA	170.239	float	[deg] Tile Right Ascension
TILEDEC	-7.093	float	[deg] Tile Declination
FIELDROT	0.0210480650645507	float	[deg] Field rotation
FA_PLAN	2022-07-01T00:00:00.000	str	[UTC] Plan field rotations for this date
FA_HA	-6.72	float	[deg] Design Hour Angle
FA_RUN	2022-01-03T17:00:31+00:00	str	[UTC] Date of the loaded Focal Plane state
FA_M_GFA	0.4	float	[mm] Margin around GFA keep-out polygons
FA_M_PET	0.4	float	[mm] Margin around petal-boundary keep-out polygons
FA_M_POS	0.05	float	[mm] Margin around positioner keep-out polygons
REQRA	170.239	float	[deg] Tile Right Ascension
REQDEC	-7.093	float	[deg] Tile Declination
FIELDNUM	0	int	Not used, always zero
FA_VER	5.4.0	str	Fiberassign code version
FA_SURV	main	str	Survey of origin of the targets

Required Data Table Columns

Name	Type	Units	Description
TARGETID	int64		Unique target ID
PETAL_LOC	int16		Petal location [0-9]
DEVICE_LOC	int32		Device location on focal plane [0-523]
LOCATION	int32		Location on the focal plane PETAL_LOC*1000 + DEVICE_LOC
FIBER	int32		Fiber ID on the CCDs [0-4999]
FIBERSTATUS	int32		Fiber status mask; 0=good
TARGET_RA	float64	deg	Target Right Ascension
TARGET_DEC	float64	deg	Target Declination
PMRA	float32	mas/yr	Proper motion in the RA direction (already including cosDEC term)
PMDEC	float32	mas/yr	Proper motion in the DEC direction
REF_EPOCH	float32	yr	Reference catalog reference epoch (eg, 2015.5 for Gaia DR2)
LAMBDA_REF	float32	Angstrom	Wavelength at which targets should be centered on fibers
FA_TARGET	int64		Targeting bit internally used by fiberassign (linked with FA_TYPE)
FA_TYPE	binary		Target type (science, standard, sky, safe, suppsky)
OBJTYPE	char[3]		TGT, SKY, BAD, empty
FIBERASSIGN_X	float32	mm	Expected CS5 X location on focal plane
FIBERASSIGN_Y	float32	mm	Expected CS5 Y location on focal plane
PRIORITY	int32		Assignment priority; larger = higher priority
SUBPRIORITY	float64		Assignment subpriority [0-1]
OBSCONDITIONS	int32		Bit-coded of allowed observing conditions
RELEASE	int16		Imaging release number
BRICKNAME	char[8]		Imaging Surveys brick name
BRICKID	int32		Imaging Surveys brick ID
BRICK_OBJID	int32		Imaging surveys OBJID on that brick
MORPHTYPE	char[4]		Imaging surveys morphological type
EBV	float32	mag	Galactic extinction E(B-V) reddening
FLUX_G	float32	nanomaggy	Flux in g-band
FLUX_R	float32	nanomaggy	Flux in r-band
FLUX_Z	float32	nanomaggy	Flux in z-band
FLUX_W1	float32	nanomaggy	Flux in WISE W1-band
FLUX_W2	float32	nanomaggy	Flux in WISE W2-band
FLUX_IVAR_G	float32	nanomaggy^-2	Inverse variance of FLUX_G
FLUX_IVAR_R	float32	nanomaggy^-2	Inverse variance of FLUX_R
FLUX_IVAR_Z	float32	nanomaggy^-2	Inverse variance of FLUX_Z
FLUX_IVAR_W1	float32	nanomaggy^-2	Inverse variance of FLUX_W1
FLUX_IVAR_W2	float32	nanomaggy^-2	Inverse variance of FLUX_W2
FIBERFLUX_G	float32	nanomaggy	g-band object model flux for 1 arcsec seeing and 1.5 arcsec diameter fiber
FIBERFLUX_R	float32	nanomaggy	r-band object model flux for 1 arcsec seeing and 1.5 arcsec diameter fiber
FIBERFLUX_Z	float32	nanomaggy	z-band object model flux for 1 arcsec seeing and 1.5 arcsec diameter fiber
FIBERTOTFLUX_G	float32	nanomaggy	like FIBERFLUX_G but including all objects overlapping this location
FIBERTOTFLUX_R	float32	nanomaggy	like FIBERFLUX_R but including all objects overlapping this location
FIBERTOTFLUX_Z	float32	nanomaggy	like FIBERFLUX_Z but including all objects overlapping this location
MASKBITS	int16		Bitwise mask from the imaging indicating potential issue or blending
SERSIC	float32		Power-law index for the Sersic profile model
SHAPE_R	float32	arcsec	Half-light radius of galaxy model for galaxy type
SHAPE_E1	float32		Ellipticity component 1 of galaxy model for galaxy type
SHAPE_E2	float32		Ellipticity component 2 of galaxy model for galaxy type
REF_ID	int64		Astrometric catalog reference ID (SOURCE_ID from Gaia and SGA; built from TYC1, TYC2, TYC3 for Tycho2)
REF_CAT	char[2]		Reference catalog source for this star
GAIA_PHOT_G_MEAN_MAG	float32	mag	Gaia G band mag
GAIA_PHOT_BP_MEAN_MAG	float32	mag	Gaia BP mag
GAIA_PHOT_RP_MEAN_MAG	float32	mag	Gaia RP mag
PARALLAX	float32	mas	Reference catalog parallax
PHOTSYS	char[1]		‘N’ for the MzLS/BASS photometric system, ‘S’ for DECaLS, ‘G’ for Gaia, ‘’ for stuck/broken fibers
PRIORITY_INIT	int64		Initial priority for target calculated across target selection bitmasks and OBSCONDITIONS
NUMOBS_INIT	int64		Initial number of observations for target calculated across target selection bitmasks and OBSCONDITIONS
DESI_TARGET	int64		Dark survey + calibration bitmask
BGS_TARGET	int64		Bright Galaxy Survey bitmask
MWS_TARGET	int64		Milky Way Survey bitmask
SCND_TARGET	int64		Secondary programs bitmask
PLATE_RA	float64	deg	Right Ascension to be used by PlateMaker
PLATE_DEC	float64	deg	Declination to be used by PlateMaker

HDU2

EXTNAME = SKY_MONITOR

Blank sky assignments for sky monitor positioners.

Required Header Keywords

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	99	int	width of table in bytes
NAXIS2	20	int	number of rows in table
TILEID	4403	int	Tile ID
TILERA	170.239	float	[deg] Tile Right Ascension
TILEDEC	-7.093	float	[deg] Tile Declination
FIELDROT	0.0210480650645507	float	[deg] Field rotation
FA_PLAN	2022-07-01T00:00:00.000	str	[UTC] Plan field rotations for this date
FA_HA	-6.72	float	[deg] Design Hour Angle
FA_RUN	2022-01-03T17:00:31+00:00	str	[UTC] Date of the loaded Focal Plane state
FA_M_GFA	0.4	float	[mm] Margin around GFA keep-out polygons
FA_M_PET	0.4	float	[mm] Margin around petal-boundary keep-out polygons
FA_M_POS	0.05	float	[mm] Margin around positioner keep-out polygons
REQRA	170.239	float	[deg] Tile Right Ascension
REQDEC	-7.093	float	[deg] Tile Declination
FIELDNUM	0	int	Not used, always zero
FA_VER	5.4.0	str	Fiberassign code version
FA_SURV	main	str	Survey of origin of the targets

Required Data Table Columns

Name	Type	Units	Description
FIBER	int32		Fiber ID on the CCDs [0-4999]
LOCATION	int32		Location on the focal plane PETAL_LOC*1000 + DEVICE_LOC
TARGETID	int64		Unique target ID
BRICKID	int32		Imaging Surveys brick ID
BRICK_OBJID	int32		Imaging surveys OBJID on that brick
FA_TARGET	int64		Targeting bit internally used by fiberassign (linked with FA_TYPE)
FA_TYPE	binary		Target type (science, standard, sky, safe, suppsky)
TARGET_RA	float64	deg	Target Right Ascension
TARGET_DEC	float64	deg	Target Declination
FIBERASSIGN_X	float32	mm	Expected CS5 X location on focal plane
FIBERASSIGN_Y	float32	mm	Expected CS5 Y location on focal plane
BRICKNAME	char[8]		Imaging Surveys brick name
FIBERSTATUS	int32		Fiber status mask; 0=good
PETAL_LOC	int16		Petal location [0-9]
DEVICE_LOC	int32		Device location on focal plane [0-523]
PRIORITY	int32		Assignment priority; larger = higher priority
SUBPRIORITY	float64		Assignment subpriority [0-1]
FIBERFLUX_G	float32	nanomaggy	Flux in g-band
FIBERFLUX_R	float32	nanomaggy	Flux in r-band
FIBERFLUX_Z	float32	nanomaggy	Flux in z-band

HDU3

EXTNAME = GFA_TARGETS

GFA stars to be used by the ETC / GUIDE / FOCUS

Required Header Keywords

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	172	int	width of table in bytes
NAXIS2	988	int	number of rows in table
TILEID	4403	int	Tile ID
TILERA	170.239	float	[deg] Tile Right Ascension
TILEDEC	-7.093	float	[deg] Tile Declination
FIELDROT	0.0210480650645507	float	[deg] Field rotation
FA_PLAN	2022-07-01T00:00:00.000	str	[UTC] Plan field rotations for this date
FA_HA	-6.72	float	[deg] Design Hour Angle
FA_RUN	2022-01-03T17:00:31+00:00	str	[UTC] Date of the loaded Focal Plane state
FA_M_GFA	0.4	float	[mm] Margin around GFA keep-out polygons
FA_M_PET	0.4	float	[mm] Margin around petal-boundary keep-out polygons
FA_M_POS	0.05	float	[mm] Margin around positioner keep-out polygons
REQRA	170.239	float	[deg] Tile Right Ascension
REQDEC	-7.093	float	[deg] Tile Declination
FIELDNUM	0	int	Not used, always zero
FA_VER	5.4.0	str	Fiberassign code version
FA_SURV	main	str	Survey of origin of the targets

Required Data Table Columns

Name	Type	Units	Description
RELEASE	int32		Imaging release number
TARGETID	int64		Unique target ID
BRICKID	int32		Imaging Surveys brick ID
BRICK_OBJID	int32		Imaging surveys OBJID on that brick
TARGET_RA	float64	deg	Target Right Ascension
TARGET_DEC	float64	deg	Target Declination
TARGET_RA_IVAR	float32	deg^-2	Inverse variance of TARGET_RA
TARGET_DEC_IVAR	float32	deg^-2	Inverse variance of TARGET_DEC
MORPHTYPE	char[4]		Imaging surveys morphological type
MASKBITS	int16		Bitwise mask from the imaging indicating potential issue or blending
FLUX_G	float32	nanomaggy	Flux in g-band
FLUX_R	float32	nanomaggy	Flux in r-band
FLUX_Z	float32	nanomaggy	Flux in z-band
FLUX_IVAR_G	float32	nanomaggy^-2	Inverse variance of FLUX_G
FLUX_IVAR_R	float32	nanomaggy^-2	Inverse variance of FLUX_R
FLUX_IVAR_Z	float32	nanomaggy^-2	Inverse variance of FLUX_Z
REF_ID	int64		Astrometric catalog reference ID (SOURCE_ID from Gaia and SGA; built from TYC1, TYC2, TYC3 for Tycho2)
REF_CAT	char[2]		Reference catalog source for this star
REF_EPOCH	float32	yr	Reference catalog reference epoch
PARALLAX	float32	mas	Reference catalog parallax
PARALLAX_IVAR	float32	mas^-2	Inverse variance of PARALLAX
PMRA	float32	mas/yr	Proper motion in the RA direction (already including cosDEC term)
PMDEC	float32	mas/yr	Proper motion in the DEC direction
PMRA_IVAR	float32	yr^2/mas^2	Inverse variance of PMRA
PMDEC_IVAR	float32	yr^2/mas^2	Inverse variance of PMDEC
GAIA_PHOT_G_MEAN_MAG	float32	mag	Gaia G band mag
GAIA_PHOT_G_MEAN_FLUX_OVER_ERROR	float32		Gaia G band signal-to-noise
GAIA_PHOT_BP_MEAN_MAG	float32	mag	Gaia BP band mag
GAIA_PHOT_BP_MEAN_FLUX_OVER_ERROR	float32		Gaia BP signal-to-noise
GAIA_PHOT_RP_MEAN_MAG	float32	mag	Gaia RP band mag
GAIA_PHOT_RP_MEAN_FLUX_OVER_ERROR	float32		Gaia RP signal-to-noise
GAIA_ASTROMETRIC_EXCESS_NOISE	float32		Gaia astrometric excess noise
URAT_ID	int64		URAT ID
URAT_SEP	float32	arcsec	Distance separation to the URAT coordinates
GAIA_PHOT_G_N_OBS	int32		Gaia G band number of observations
HPXPIXEL	int64		HEALPixel containing GFA target
GFA_LOC	int16		Covered GFA identifier
GUIDE_FLAG	int16		GUIDING bitmask
FOCUS_FLAG	int16		FOCUS bitmask
ETC_FLAG	int16		ETC bitmask

HDU4

EXTNAME = TARGETS

Unique list of targets reachable by a positioner.

Required Header Keywords

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	81	int	width of table in bytes
NAXIS2	152687	int	number of rows in table
TILEID	4403	int	Tile ID
TILERA	170.239	float	[deg] Tile Right Ascension
TILEDEC	-7.093	float	[deg] Tile Declination
FIELDROT	0.0210480650645507	float	[deg] Field rotation
FA_PLAN	2022-07-01T00:00:00.000	str	[UTC] Plan field rotations for this date
FA_HA	-6.72	float	[deg] Design Hour Angle
FA_RUN	2022-01-03T17:00:31+00:00	str	[UTC] Date of the loaded Focal Plane state
FA_M_GFA	0.4	float	[mm] Margin around GFA keep-out polygons
FA_M_PET	0.4	float	[mm] Margin around petal-boundary keep-out polygons
FA_M_POS	0.05	float	[mm] Margin around positioner keep-out polygons
REQRA	170.239	float	[deg] Tile Right Ascension
REQDEC	-7.093	float	[deg] Tile Declination
FIELDNUM	0	int	Not used, always zero
FA_VER	5.4.0	str	Fiberassign code version
FA_SURV	main	str	Survey of origin of the targets

Required Data Table Columns

Name	Type	Units	Description
TARGETID	int64		Unique target ID
RA	float64	deg	Target Right Ascension
DEC	float64	deg	Target Declination
FA_TARGET	int64		Targeting bit internally used by fiberassign (linked with FA_TYPE)
FA_TYPE	binary		Target type (science, standard, sky, safe, suppsky)
PRIORITY	int32		Assignment priority; larger = higher priority
SUBPRIORITY	float64		Assignment subpriority [0-1]
OBSCONDITIONS	int32		Bit-coded of allowed observing conditions
DESI_TARGET	int64		Dark survey + calibration bitmask
BGS_TARGET	int64		Bright Galaxy Survey bitmask
MWS_TARGET	int64		Milky Way Survey bitmask
SCND_TARGET	int64		Secondary programs bitmask

HDU5

EXTNAME = POTENTIAL_ASSIGNMENTS

A list of targets that could have been assigned to each fiber.

Required Header Keywords

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	16	int	width of table in bytes
NAXIS2	169775	int	number of rows in table
TILEID	4403	int	Tile ID
TILERA	170.239	float	[deg] Tile Right Ascension
TILEDEC	-7.093	float	[deg] Tile Declination
FIELDROT	0.0210480650645507	float	[deg] Field rotation
FA_PLAN	2022-07-01T00:00:00.000	str	[UTC] Plan field rotations for this date
FA_HA	-6.72	float	[deg] Design Hour Angle
FA_RUN	2022-01-03T17:00:31+00:00	str	[UTC] Date of the loaded Focal Plane state
FA_M_GFA	0.4	float	[mm] Margin around GFA keep-out polygons
FA_M_PET	0.4	float	[mm] Margin around petal-boundary keep-out polygons
FA_M_POS	0.05	float	[mm] Margin around positioner keep-out polygons
REQRA	170.239	float	[deg] Tile Right Ascension
REQDEC	-7.093	float	[deg] Tile Declination
FIELDNUM	0	int	Not used, always zero
FA_VER	5.4.0	str	Fiberassign code version
FA_SURV	main	str	Survey of origin of the targets

Required Data Table Columns

Name	Type	Units	Description
TARGETID	int64		Unique target ID
FIBER	int32		Fiber ID on the CCDs [0-4999]
LOCATION	int32		Location on the focal plane PETAL_LOC*1000 + DEVICE_LOC

Notes and Examples

For the SURVEY=cmx m33 tile (TILEID=80615) tile and all the SURVEY=sv1 tiles (except TILEID=80971-80976, the dc3r2 ones), proper-motion correction was applied at the fiberassign design step; thus the following columns can have different values than in the desitarget products: TARGET_RA, TARGET_DEC, REF_EPOCH, PLATE_RA, PLATE_DEC, and PLATE_REF_EPOCH.

• HDU0: early tiles may have some missing keywords from the listed ones.

• HDU1: this table defines the requested fiber assignments; see fibermap-EXPID for the actual observed assignments.

• HDU1: LAMBDA_REF : 5400 so far, not used for fiber positioning.

• HDU1, HDU4, HDU5: files built from CMX, SV1, SV2, or SV3 targets will have a slightly different column content for the targetings bit columns (e.g., CMX_TARGET, SV1_DESI_TARGET).

• HDU2: BRICKID, BRICK_OBJID, FA_TARGET, BRICKNAME, PRIORITY, SUBPRIORITY, FIBERFLUX_G, FIBERFLUX_R, FIBERFLUX_Z mostly are a zero value (and an empty string for BRICKNAME).

• HDU3: for objects that do not have a match in URAT, the URAT_ID and URAT_SEP columns are -1.

• HDU5: the same target can appear more than once if it is reachable by more than one fiber.